mySQL 5.0.11 sources for tomato

[tomato.git] / release / src / router / mysql / storage / innodb_plugin / row / row0sel.c

/*****************************************************************************

Copyright (c) 1997, 2013, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2008, Google Inc.

Portions of this file contain modifications contributed and copyrighted by
Google, Inc. Those modifications are gratefully acknowledged and are described
briefly in the InnoDB documentation. The contributions by Google are
incorporated with their permission, and subject to the conditions contained in
the file COPYING.Google.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 
51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

*****************************************************************************/

/***************************************************//**
@file row/row0sel.c
Select

Created 12/19/1997 Heikki Tuuri
*******************************************************/

#include "row0sel.h"

#ifdef UNIV_NONINL
#include "row0sel.ic"
#endif

#include "dict0dict.h"
#include "dict0boot.h"
#include "trx0undo.h"
#include "trx0trx.h"
#include "btr0btr.h"
#include "btr0cur.h"
#include "btr0sea.h"
#include "mach0data.h"
#include "que0que.h"
#include "row0upd.h"
#include "row0row.h"
#include "row0vers.h"
#include "rem0cmp.h"
#include "lock0lock.h"
#include "eval0eval.h"
#include "pars0sym.h"
#include "pars0pars.h"
#include "row0mysql.h"
#include "read0read.h"
#include "buf0lru.h"
#include "ha_prototypes.h"
#ifdef __WIN__
/* error LNK2001: unresolved external symbol _debug_sync_C_callback_ptr */
# define DEBUG_SYNC_C(dummy) ((void) 0)
#else
#include "m_string.h" /* for my_sys.h */
#include "my_sys.h" /* DEBUG_SYNC_C */
#endif

/* Maximum number of rows to prefetch; MySQL interface has another parameter */
#define SEL_MAX_N_PREFETCH      16

/* Number of rows fetched, after which to start prefetching; MySQL interface
has another parameter */
#define SEL_PREFETCH_LIMIT      1

/* When a select has accessed about this many pages, it returns control back
to que_run_threads: this is to allow canceling runaway queries */

#define SEL_COST_LIMIT  100

/* Flags for search shortcut */
#define SEL_FOUND       0
#define SEL_EXHAUSTED   1
#define SEL_RETRY       2

/********************************************************************//**
Returns TRUE if the user-defined column in a secondary index record
is alphabetically the same as the corresponding BLOB column in the clustered
index record.
NOTE: the comparison is NOT done as a binary comparison, but character
fields are compared with collation!
@return TRUE if the columns are equal */
static
ibool
row_sel_sec_rec_is_for_blob(
/*========================*/
        ulint           mtype,          /*!< in: main type */
        ulint           prtype,         /*!< in: precise type */
        ulint           mbminlen,       /*!< in: minimum length of a
                                        multi-byte character */
        ulint           mbmaxlen,       /*!< in: maximum length of a
                                        multi-byte character */
        const byte*     clust_field,    /*!< in: the locally stored part of
                                        the clustered index column, including
                                        the BLOB pointer; the clustered
                                        index record must be covered by
                                        a lock or a page latch to protect it
                                        against deletion (rollback or purge) */
        ulint           clust_len,      /*!< in: length of clust_field */
        const byte*     sec_field,      /*!< in: column in secondary index */
        ulint           sec_len,        /*!< in: length of sec_field */
        ulint           prefix_len,     /*!< in: index column prefix length
                                        in bytes */
        ulint           zip_size)       /*!< in: compressed page size, or 0 */
{
        ulint   len;
        byte    buf[DICT_MAX_INDEX_COL_LEN];

        ut_a(clust_len >= BTR_EXTERN_FIELD_REF_SIZE);
        ut_ad(prefix_len >= sec_len);
        ut_ad(prefix_len > 0);
        ut_a(prefix_len <= sizeof buf);

        if (UNIV_UNLIKELY
            (!memcmp(clust_field + clust_len - BTR_EXTERN_FIELD_REF_SIZE,
                     field_ref_zero, BTR_EXTERN_FIELD_REF_SIZE))) {
                /* The externally stored field was not written yet.
                This record should only be seen by
                recv_recovery_rollback_active() or any
                TRX_ISO_READ_UNCOMMITTED transactions. */
                return(FALSE);
        }

        len = btr_copy_externally_stored_field_prefix(buf, prefix_len,
                                                      zip_size,
                                                      clust_field, clust_len);

        if (UNIV_UNLIKELY(len == 0)) {
                /* The BLOB was being deleted as the server crashed.
                There should not be any secondary index records
                referring to this clustered index record, because
                btr_free_externally_stored_field() is called after all
                secondary index entries of the row have been purged. */
                return(FALSE);
        }

        len = dtype_get_at_most_n_mbchars(prtype, mbminlen, mbmaxlen,
                                          prefix_len, len, (const char*) buf);

        return(!cmp_data_data(mtype, prtype, buf, len, sec_field, sec_len));
}

/********************************************************************//**
Returns TRUE if the user-defined column values in a secondary index record
are alphabetically the same as the corresponding columns in the clustered
index record.
NOTE: the comparison is NOT done as a binary comparison, but character
fields are compared with collation!
@return TRUE if the secondary record is equal to the corresponding
fields in the clustered record, when compared with collation;
FALSE if not equal or if the clustered record has been marked for deletion */
static
ibool
row_sel_sec_rec_is_for_clust_rec(
/*=============================*/
        const rec_t*    sec_rec,        /*!< in: secondary index record */
        dict_index_t*   sec_index,      /*!< in: secondary index */
        const rec_t*    clust_rec,      /*!< in: clustered index record;
                                        must be protected by a lock or
                                        a page latch against deletion
                                        in rollback or purge */
        dict_index_t*   clust_index)    /*!< in: clustered index */
{
        const byte*     sec_field;
        ulint           sec_len;
        const byte*     clust_field;
        ulint           n;
        ulint           i;
        mem_heap_t*     heap            = NULL;
        ulint           clust_offsets_[REC_OFFS_NORMAL_SIZE];
        ulint           sec_offsets_[REC_OFFS_SMALL_SIZE];
        ulint*          clust_offs      = clust_offsets_;
        ulint*          sec_offs        = sec_offsets_;
        ibool           is_equal        = TRUE;

        rec_offs_init(clust_offsets_);
        rec_offs_init(sec_offsets_);

        if (rec_get_deleted_flag(clust_rec,
                                 dict_table_is_comp(clust_index->table))) {

                /* The clustered index record is delete-marked;
                it is not visible in the read view.  Besides,
                if there are any externally stored columns,
                some of them may have already been purged. */
                return(FALSE);
        }

        clust_offs = rec_get_offsets(clust_rec, clust_index, clust_offs,
                                     ULINT_UNDEFINED, &heap);
        sec_offs = rec_get_offsets(sec_rec, sec_index, sec_offs,
                                   ULINT_UNDEFINED, &heap);

        n = dict_index_get_n_ordering_defined_by_user(sec_index);

        for (i = 0; i < n; i++) {
                const dict_field_t*     ifield;
                const dict_col_t*       col;
                ulint                   clust_pos;
                ulint                   clust_len;
                ulint                   len;

                ifield = dict_index_get_nth_field(sec_index, i);
                col = dict_field_get_col(ifield);
                clust_pos = dict_col_get_clust_pos(col, clust_index);

                clust_field = rec_get_nth_field(
                        clust_rec, clust_offs, clust_pos, &clust_len);
                sec_field = rec_get_nth_field(sec_rec, sec_offs, i, &sec_len);

                len = clust_len;

                if (ifield->prefix_len > 0 && len != UNIV_SQL_NULL
                    && sec_len != UNIV_SQL_NULL) {

                        if (rec_offs_nth_extern(clust_offs, clust_pos)) {
                                len -= BTR_EXTERN_FIELD_REF_SIZE;
                        }

                        len = dtype_get_at_most_n_mbchars(
                                col->prtype, col->mbminlen, col->mbmaxlen,
                                ifield->prefix_len, len, (char*) clust_field);

                        if (rec_offs_nth_extern(clust_offs, clust_pos)
                            && len < sec_len) {
                                /* This function should never be
                                invoked on an Antelope format table,
                                because they should always contain
                                enough prefix in the clustered index
                                record. */
                                ut_ad(dict_table_get_format(clust_index->table)
                                      >= DICT_TF_FORMAT_ZIP);

                                if (!row_sel_sec_rec_is_for_blob(
                                            col->mtype, col->prtype,
                                            col->mbminlen, col->mbmaxlen,
                                            clust_field, clust_len,
                                            sec_field, sec_len,
                                            ifield->prefix_len,
                                            dict_table_zip_size(
                                                    clust_index->table))) {
                                        goto inequal;
                                }

                                continue;
                        }
                }

                if (0 != cmp_data_data(col->mtype, col->prtype,
                                       clust_field, len,
                                       sec_field, sec_len)) {
inequal:
                        is_equal = FALSE;
                        goto func_exit;
                }
        }

func_exit:
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }
        return(is_equal);
}

/*********************************************************************//**
Creates a select node struct.
@return own: select node struct */
UNIV_INTERN
sel_node_t*
sel_node_create(
/*============*/
        mem_heap_t*     heap)   /*!< in: memory heap where created */
{
        sel_node_t*     node;

        node = mem_heap_alloc(heap, sizeof(sel_node_t));
        node->common.type = QUE_NODE_SELECT;
        node->state = SEL_NODE_OPEN;

        node->plans = NULL;

        return(node);
}

/*********************************************************************//**
Frees the memory private to a select node when a query graph is freed,
does not free the heap where the node was originally created. */
UNIV_INTERN
void
sel_node_free_private(
/*==================*/
        sel_node_t*     node)   /*!< in: select node struct */
{
        ulint   i;
        plan_t* plan;

        if (node->plans != NULL) {
                for (i = 0; i < node->n_tables; i++) {
                        plan = sel_node_get_nth_plan(node, i);

                        btr_pcur_close(&(plan->pcur));
                        btr_pcur_close(&(plan->clust_pcur));

                        if (plan->old_vers_heap) {
                                mem_heap_free(plan->old_vers_heap);
                        }
                }
        }
}

/*********************************************************************//**
Evaluates the values in a select list. If there are aggregate functions,
their argument value is added to the aggregate total. */
UNIV_INLINE
void
sel_eval_select_list(
/*=================*/
        sel_node_t*     node)   /*!< in: select node */
{
        que_node_t*     exp;

        exp = node->select_list;

        while (exp) {
                eval_exp(exp);

                exp = que_node_get_next(exp);
        }
}

/*********************************************************************//**
Assigns the values in the select list to the possible into-variables in
SELECT ... INTO ... */
UNIV_INLINE
void
sel_assign_into_var_values(
/*=======================*/
        sym_node_t*     var,    /*!< in: first variable in a list of variables */
        sel_node_t*     node)   /*!< in: select node */
{
        que_node_t*     exp;

        if (var == NULL) {

                return;
        }

        exp = node->select_list;

        while (var) {
                ut_ad(exp);

                eval_node_copy_val(var->alias, exp);

                exp = que_node_get_next(exp);
                var = que_node_get_next(var);
        }
}

/*********************************************************************//**
Resets the aggregate value totals in the select list of an aggregate type
query. */
UNIV_INLINE
void
sel_reset_aggregate_vals(
/*=====================*/
        sel_node_t*     node)   /*!< in: select node */
{
        func_node_t*    func_node;

        ut_ad(node->is_aggregate);

        func_node = node->select_list;

        while (func_node) {
                eval_node_set_int_val(func_node, 0);

                func_node = que_node_get_next(func_node);
        }

        node->aggregate_already_fetched = FALSE;
}

/*********************************************************************//**
Copies the input variable values when an explicit cursor is opened. */
UNIV_INLINE
void
row_sel_copy_input_variable_vals(
/*=============================*/
        sel_node_t*     node)   /*!< in: select node */
{
        sym_node_t*     var;

        var = UT_LIST_GET_FIRST(node->copy_variables);

        while (var) {
                eval_node_copy_val(var, var->alias);

                var->indirection = NULL;

                var = UT_LIST_GET_NEXT(col_var_list, var);
        }
}

/*********************************************************************//**
Fetches the column values from a record. */
static
void
row_sel_fetch_columns(
/*==================*/
        dict_index_t*   index,  /*!< in: record index */
        const rec_t*    rec,    /*!< in: record in a clustered or non-clustered
                                index; must be protected by a page latch */
        const ulint*    offsets,/*!< in: rec_get_offsets(rec, index) */
        sym_node_t*     column) /*!< in: first column in a column list, or
                                NULL */
{
        dfield_t*       val;
        ulint           index_type;
        ulint           field_no;
        const byte*     data;
        ulint           len;

        ut_ad(rec_offs_validate(rec, index, offsets));

        if (dict_index_is_clust(index)) {
                index_type = SYM_CLUST_FIELD_NO;
        } else {
                index_type = SYM_SEC_FIELD_NO;
        }

        while (column) {
                mem_heap_t*     heap = NULL;
                ibool           needs_copy;

                field_no = column->field_nos[index_type];

                if (field_no != ULINT_UNDEFINED) {

                        if (UNIV_UNLIKELY(rec_offs_nth_extern(offsets,
                                                              field_no))) {

                                /* Copy an externally stored field to the
                                temporary heap, if possible. */

                                heap = mem_heap_create(1);

                                data = btr_rec_copy_externally_stored_field(
                                        rec, offsets,
                                        dict_table_zip_size(index->table),
                                        field_no, &len, heap);

                                /* data == NULL means that the
                                externally stored field was not
                                written yet. This record
                                should only be seen by
                                recv_recovery_rollback_active() or any
                                TRX_ISO_READ_UNCOMMITTED
                                transactions. The InnoDB SQL parser
                                (the sole caller of this function)
                                does not implement READ UNCOMMITTED,
                                and it is not involved during rollback. */
                                ut_a(data);
                                ut_a(len != UNIV_SQL_NULL);

                                needs_copy = TRUE;
                        } else {
                                data = rec_get_nth_field(rec, offsets,
                                                         field_no, &len);

                                needs_copy = column->copy_val;
                        }

                        if (needs_copy) {
                                eval_node_copy_and_alloc_val(column, data,
                                                             len);
                        } else {
                                val = que_node_get_val(column);
                                dfield_set_data(val, data, len);
                        }

                        if (UNIV_LIKELY_NULL(heap)) {
                                mem_heap_free(heap);
                        }
                }

                column = UT_LIST_GET_NEXT(col_var_list, column);
        }
}

/*********************************************************************//**
Allocates a prefetch buffer for a column when prefetch is first time done. */
static
void
sel_col_prefetch_buf_alloc(
/*=======================*/
        sym_node_t*     column) /*!< in: symbol table node for a column */
{
        sel_buf_t*      sel_buf;
        ulint           i;

        ut_ad(que_node_get_type(column) == QUE_NODE_SYMBOL);

        column->prefetch_buf = mem_alloc(SEL_MAX_N_PREFETCH
                                         * sizeof(sel_buf_t));
        for (i = 0; i < SEL_MAX_N_PREFETCH; i++) {
                sel_buf = column->prefetch_buf + i;

                sel_buf->data = NULL;
                sel_buf->len = 0;
                sel_buf->val_buf_size = 0;
        }
}

/*********************************************************************//**
Frees a prefetch buffer for a column, including the dynamically allocated
memory for data stored there. */
UNIV_INTERN
void
sel_col_prefetch_buf_free(
/*======================*/
        sel_buf_t*      prefetch_buf)   /*!< in, own: prefetch buffer */
{
        sel_buf_t*      sel_buf;
        ulint           i;

        for (i = 0; i < SEL_MAX_N_PREFETCH; i++) {
                sel_buf = prefetch_buf + i;

                if (sel_buf->val_buf_size > 0) {

                        mem_free(sel_buf->data);
                }
        }

        mem_free(prefetch_buf);
}

/*********************************************************************//**
Pops the column values for a prefetched, cached row from the column prefetch
buffers and places them to the val fields in the column nodes. */
static
void
sel_pop_prefetched_row(
/*===================*/
        plan_t* plan)   /*!< in: plan node for a table */
{
        sym_node_t*     column;
        sel_buf_t*      sel_buf;
        dfield_t*       val;
        byte*           data;
        ulint           len;
        ulint           val_buf_size;

        ut_ad(plan->n_rows_prefetched > 0);

        column = UT_LIST_GET_FIRST(plan->columns);

        while (column) {
                val = que_node_get_val(column);

                if (!column->copy_val) {
                        /* We did not really push any value for the
                        column */

                        ut_ad(!column->prefetch_buf);
                        ut_ad(que_node_get_val_buf_size(column) == 0);
                        ut_d(dfield_set_null(val));

                        goto next_col;
                }

                ut_ad(column->prefetch_buf);
                ut_ad(!dfield_is_ext(val));

                sel_buf = column->prefetch_buf + plan->first_prefetched;

                data = sel_buf->data;
                len = sel_buf->len;
                val_buf_size = sel_buf->val_buf_size;

                /* We must keep track of the allocated memory for
                column values to be able to free it later: therefore
                we swap the values for sel_buf and val */

                sel_buf->data = dfield_get_data(val);
                sel_buf->len = dfield_get_len(val);
                sel_buf->val_buf_size = que_node_get_val_buf_size(column);

                dfield_set_data(val, data, len);
                que_node_set_val_buf_size(column, val_buf_size);
next_col:
                column = UT_LIST_GET_NEXT(col_var_list, column);
        }

        plan->n_rows_prefetched--;

        plan->first_prefetched++;
}

/*********************************************************************//**
Pushes the column values for a prefetched, cached row to the column prefetch
buffers from the val fields in the column nodes. */
UNIV_INLINE
void
sel_push_prefetched_row(
/*====================*/
        plan_t* plan)   /*!< in: plan node for a table */
{
        sym_node_t*     column;
        sel_buf_t*      sel_buf;
        dfield_t*       val;
        byte*           data;
        ulint           len;
        ulint           pos;
        ulint           val_buf_size;

        if (plan->n_rows_prefetched == 0) {
                pos = 0;
                plan->first_prefetched = 0;
        } else {
                pos = plan->n_rows_prefetched;

                /* We have the convention that pushing new rows starts only
                after the prefetch stack has been emptied: */

                ut_ad(plan->first_prefetched == 0);
        }

        plan->n_rows_prefetched++;

        ut_ad(pos < SEL_MAX_N_PREFETCH);

        column = UT_LIST_GET_FIRST(plan->columns);

        while (column) {
                if (!column->copy_val) {
                        /* There is no sense to push pointers to database
                        page fields when we do not keep latch on the page! */

                        goto next_col;
                }

                if (!column->prefetch_buf) {
                        /* Allocate a new prefetch buffer */

                        sel_col_prefetch_buf_alloc(column);
                }

                sel_buf = column->prefetch_buf + pos;

                val = que_node_get_val(column);

                data = dfield_get_data(val);
                len = dfield_get_len(val);
                val_buf_size = que_node_get_val_buf_size(column);

                /* We must keep track of the allocated memory for
                column values to be able to free it later: therefore
                we swap the values for sel_buf and val */

                dfield_set_data(val, sel_buf->data, sel_buf->len);
                que_node_set_val_buf_size(column, sel_buf->val_buf_size);

                sel_buf->data = data;
                sel_buf->len = len;
                sel_buf->val_buf_size = val_buf_size;
next_col:
                column = UT_LIST_GET_NEXT(col_var_list, column);
        }
}

/*********************************************************************//**
Builds a previous version of a clustered index record for a consistent read
@return DB_SUCCESS or error code */
static
ulint
row_sel_build_prev_vers(
/*====================*/
        read_view_t*    read_view,      /*!< in: read view */
        dict_index_t*   index,          /*!< in: plan node for table */
        rec_t*          rec,            /*!< in: record in a clustered index */
        ulint**         offsets,        /*!< in/out: offsets returned by
                                        rec_get_offsets(rec, plan->index) */
        mem_heap_t**    offset_heap,    /*!< in/out: memory heap from which
                                        the offsets are allocated */
        mem_heap_t**    old_vers_heap,  /*!< out: old version heap to use */
        rec_t**         old_vers,       /*!< out: old version, or NULL if the
                                        record does not exist in the view:
                                        i.e., it was freshly inserted
                                        afterwards */
        mtr_t*          mtr)            /*!< in: mtr */
{
        ulint   err;

        if (*old_vers_heap) {
                mem_heap_empty(*old_vers_heap);
        } else {
                *old_vers_heap = mem_heap_create(512);
        }

        err = row_vers_build_for_consistent_read(
                rec, mtr, index, offsets, read_view, offset_heap,
                *old_vers_heap, old_vers);
        return(err);
}

/*********************************************************************//**
Builds the last committed version of a clustered index record for a
semi-consistent read.
@return DB_SUCCESS or error code */
static
ulint
row_sel_build_committed_vers_for_mysql(
/*===================================*/
        dict_index_t*   clust_index,    /*!< in: clustered index */
        row_prebuilt_t* prebuilt,       /*!< in: prebuilt struct */
        const rec_t*    rec,            /*!< in: record in a clustered index */
        ulint**         offsets,        /*!< in/out: offsets returned by
                                        rec_get_offsets(rec, clust_index) */
        mem_heap_t**    offset_heap,    /*!< in/out: memory heap from which
                                        the offsets are allocated */
        const rec_t**   old_vers,       /*!< out: old version, or NULL if the
                                        record does not exist in the view:
                                        i.e., it was freshly inserted
                                        afterwards */
        mtr_t*          mtr)            /*!< in: mtr */
{
        ulint   err;

        if (prebuilt->old_vers_heap) {
                mem_heap_empty(prebuilt->old_vers_heap);
        } else {
                prebuilt->old_vers_heap = mem_heap_create(200);
        }

        err = row_vers_build_for_semi_consistent_read(
                rec, mtr, clust_index, offsets, offset_heap,
                prebuilt->old_vers_heap, old_vers);
        return(err);
}

/*********************************************************************//**
Tests the conditions which determine when the index segment we are searching
through has been exhausted.
@return TRUE if row passed the tests */
UNIV_INLINE
ibool
row_sel_test_end_conds(
/*===================*/
        plan_t* plan)   /*!< in: plan for the table; the column values must
                        already have been retrieved and the right sides of
                        comparisons evaluated */
{
        func_node_t*    cond;

        /* All conditions in end_conds are comparisons of a column to an
        expression */

        cond = UT_LIST_GET_FIRST(plan->end_conds);

        while (cond) {
                /* Evaluate the left side of the comparison, i.e., get the
                column value if there is an indirection */

                eval_sym(cond->args);

                /* Do the comparison */

                if (!eval_cmp(cond)) {

                        return(FALSE);
                }

                cond = UT_LIST_GET_NEXT(cond_list, cond);
        }

        return(TRUE);
}

/*********************************************************************//**
Tests the other conditions.
@return TRUE if row passed the tests */
UNIV_INLINE
ibool
row_sel_test_other_conds(
/*=====================*/
        plan_t* plan)   /*!< in: plan for the table; the column values must
                        already have been retrieved */
{
        func_node_t*    cond;

        cond = UT_LIST_GET_FIRST(plan->other_conds);

        while (cond) {
                eval_exp(cond);

                if (!eval_node_get_ibool_val(cond)) {

                        return(FALSE);
                }

                cond = UT_LIST_GET_NEXT(cond_list, cond);
        }

        return(TRUE);
}

/*********************************************************************//**
Retrieves the clustered index record corresponding to a record in a
non-clustered index. Does the necessary locking.
@return DB_SUCCESS or error code */
static
ulint
row_sel_get_clust_rec(
/*==================*/
        sel_node_t*     node,   /*!< in: select_node */
        plan_t*         plan,   /*!< in: plan node for table */
        rec_t*          rec,    /*!< in: record in a non-clustered index */
        que_thr_t*      thr,    /*!< in: query thread */
        rec_t**         out_rec,/*!< out: clustered record or an old version of
                                it, NULL if the old version did not exist
                                in the read view, i.e., it was a fresh
                                inserted version */
        mtr_t*          mtr)    /*!< in: mtr used to get access to the
                                non-clustered record; the same mtr is used to
                                access the clustered index */
{
        dict_index_t*   index;
        rec_t*          clust_rec;
        rec_t*          old_vers;
        ulint           err;
        mem_heap_t*     heap            = NULL;
        ulint           offsets_[REC_OFFS_NORMAL_SIZE];
        ulint*          offsets         = offsets_;
        rec_offs_init(offsets_);

        *out_rec = NULL;

        offsets = rec_get_offsets(rec,
                                  btr_pcur_get_btr_cur(&plan->pcur)->index,
                                  offsets, ULINT_UNDEFINED, &heap);

        row_build_row_ref_fast(plan->clust_ref, plan->clust_map, rec, offsets);

        index = dict_table_get_first_index(plan->table);

        btr_pcur_open_with_no_init(index, plan->clust_ref, PAGE_CUR_LE,
                                   BTR_SEARCH_LEAF, &plan->clust_pcur,
                                   0, mtr);

        clust_rec = btr_pcur_get_rec(&(plan->clust_pcur));

        /* Note: only if the search ends up on a non-infimum record is the
        low_match value the real match to the search tuple */

        if (!page_rec_is_user_rec(clust_rec)
            || btr_pcur_get_low_match(&(plan->clust_pcur))
            < dict_index_get_n_unique(index)) {

                ut_a(rec_get_deleted_flag(rec,
                                          dict_table_is_comp(plan->table)));
                ut_a(node->read_view);

                /* In a rare case it is possible that no clust rec is found
                for a delete-marked secondary index record: if in row0umod.c
                in row_undo_mod_remove_clust_low() we have already removed
                the clust rec, while purge is still cleaning and removing
                secondary index records associated with earlier versions of
                the clustered index record. In that case we know that the
                clustered index record did not exist in the read view of
                trx. */

                goto func_exit;
        }

        offsets = rec_get_offsets(clust_rec, index, offsets,
                                  ULINT_UNDEFINED, &heap);

        if (!node->read_view) {
                /* Try to place a lock on the index record */

                /* If innodb_locks_unsafe_for_binlog option is used
                or this session is using READ COMMITTED isolation level
                we lock only the record, i.e., next-key locking is
                not used. */
                ulint   lock_type;
                trx_t*  trx;

                trx = thr_get_trx(thr);

                if (srv_locks_unsafe_for_binlog
                    || trx->isolation_level <= TRX_ISO_READ_COMMITTED) {
                        lock_type = LOCK_REC_NOT_GAP;
                } else {
                        lock_type = LOCK_ORDINARY;
                }

                err = lock_clust_rec_read_check_and_lock(
                        0, btr_pcur_get_block(&plan->clust_pcur),
                        clust_rec, index, offsets,
                        node->row_lock_mode, lock_type, thr);

                switch (err) {
                case DB_SUCCESS:
                case DB_SUCCESS_LOCKED_REC:
                        /* Declare the variable uninitialized in Valgrind.
                        It should be set to DB_SUCCESS at func_exit. */
                        UNIV_MEM_INVALID(&err, sizeof err);
                        break;
                default:
                        goto err_exit;
                }
        } else {
                /* This is a non-locking consistent read: if necessary, fetch
                a previous version of the record */

                old_vers = NULL;

                if (!lock_clust_rec_cons_read_sees(clust_rec, index, offsets,
                                                   node->read_view)) {

                        err = row_sel_build_prev_vers(
                                node->read_view, index, clust_rec,
                                &offsets, &heap, &plan->old_vers_heap,
                                &old_vers, mtr);

                        if (err != DB_SUCCESS) {

                                goto err_exit;
                        }

                        clust_rec = old_vers;

                        if (clust_rec == NULL) {
                                goto func_exit;
                        }
                }

                /* If we had to go to an earlier version of row or the
                secondary index record is delete marked, then it may be that
                the secondary index record corresponding to clust_rec
                (or old_vers) is not rec; in that case we must ignore
                such row because in our snapshot rec would not have existed.
                Remember that from rec we cannot see directly which transaction
                id corresponds to it: we have to go to the clustered index
                record. A query where we want to fetch all rows where
                the secondary index value is in some interval would return
                a wrong result if we would not drop rows which we come to
                visit through secondary index records that would not really
                exist in our snapshot. */

                if ((old_vers
                     || rec_get_deleted_flag(rec, dict_table_is_comp(
                                                     plan->table)))
                    && !row_sel_sec_rec_is_for_clust_rec(rec, plan->index,
                                                         clust_rec, index)) {
                        goto func_exit;
                }
        }

        /* Fetch the columns needed in test conditions.  The clustered
        index record is protected by a page latch that was acquired
        when plan->clust_pcur was positioned.  The latch will not be
        released until mtr_commit(mtr). */

        ut_ad(!rec_get_deleted_flag(clust_rec, rec_offs_comp(offsets)));
        row_sel_fetch_columns(index, clust_rec, offsets,
                              UT_LIST_GET_FIRST(plan->columns));
        *out_rec = clust_rec;
func_exit:
        err = DB_SUCCESS;
err_exit:
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }
        return(err);
}

/*********************************************************************//**
Sets a lock on a record.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, or error code */
UNIV_INLINE
enum db_err
sel_set_rec_lock(
/*=============*/
        const buf_block_t*      block,  /*!< in: buffer block of rec */
        const rec_t*            rec,    /*!< in: record */
        dict_index_t*           index,  /*!< in: index */
        const ulint*            offsets,/*!< in: rec_get_offsets(rec, index) */
        ulint                   mode,   /*!< in: lock mode */
        ulint                   type,   /*!< in: LOCK_ORDINARY, LOCK_GAP, or
                                        LOC_REC_NOT_GAP */
        que_thr_t*              thr)    /*!< in: query thread */
{
        trx_t*          trx;
        enum db_err     err;

        trx = thr_get_trx(thr);

        if (UT_LIST_GET_LEN(trx->trx_locks) > 10000) {
                if (buf_LRU_buf_pool_running_out()) {

                        return(DB_LOCK_TABLE_FULL);
                }
        }

        if (dict_index_is_clust(index)) {
                err = lock_clust_rec_read_check_and_lock(
                        0, block, rec, index, offsets, mode, type, thr);
        } else {
                err = lock_sec_rec_read_check_and_lock(
                        0, block, rec, index, offsets, mode, type, thr);
        }

        return(err);
}

/*********************************************************************//**
Opens a pcur to a table index. */
static
void
row_sel_open_pcur(
/*==============*/
        plan_t*         plan,           /*!< in: table plan */
        ibool           search_latch_locked,
                                        /*!< in: TRUE if the thread currently
                                        has the search latch locked in
                                        s-mode */
        mtr_t*          mtr)            /*!< in: mtr */
{
        dict_index_t*   index;
        func_node_t*    cond;
        que_node_t*     exp;
        ulint           n_fields;
        ulint           has_search_latch = 0;   /* RW_S_LATCH or 0 */
        ulint           i;

        if (search_latch_locked) {
                has_search_latch = RW_S_LATCH;
        }

        index = plan->index;

        /* Calculate the value of the search tuple: the exact match columns
        get their expressions evaluated when we evaluate the right sides of
        end_conds */

        cond = UT_LIST_GET_FIRST(plan->end_conds);

        while (cond) {
                eval_exp(que_node_get_next(cond->args));

                cond = UT_LIST_GET_NEXT(cond_list, cond);
        }

        if (plan->tuple) {
                n_fields = dtuple_get_n_fields(plan->tuple);

                if (plan->n_exact_match < n_fields) {
                        /* There is a non-exact match field which must be
                        evaluated separately */

                        eval_exp(plan->tuple_exps[n_fields - 1]);
                }

                for (i = 0; i < n_fields; i++) {
                        exp = plan->tuple_exps[i];

                        dfield_copy_data(dtuple_get_nth_field(plan->tuple, i),
                                         que_node_get_val(exp));
                }

                /* Open pcur to the index */

                btr_pcur_open_with_no_init(index, plan->tuple, plan->mode,
                                           BTR_SEARCH_LEAF, &plan->pcur,
                                           has_search_latch, mtr);
        } else {
                /* Open the cursor to the start or the end of the index
                (FALSE: no init) */

                btr_pcur_open_at_index_side(plan->asc, index, BTR_SEARCH_LEAF,
                                            &(plan->pcur), FALSE, mtr);
        }

        ut_ad(plan->n_rows_prefetched == 0);
        ut_ad(plan->n_rows_fetched == 0);
        ut_ad(plan->cursor_at_end == FALSE);

        plan->pcur_is_open = TRUE;
}

/*********************************************************************//**
Restores a stored pcur position to a table index.
@return TRUE if the cursor should be moved to the next record after we
return from this function (moved to the previous, in the case of a
descending cursor) without processing again the current cursor
record */
static
ibool
row_sel_restore_pcur_pos(
/*=====================*/
        plan_t*         plan,   /*!< in: table plan */
        mtr_t*          mtr)    /*!< in: mtr */
{
        ibool   equal_position;
        ulint   relative_position;

        ut_ad(!plan->cursor_at_end);

        relative_position = btr_pcur_get_rel_pos(&(plan->pcur));

        equal_position = btr_pcur_restore_position(BTR_SEARCH_LEAF,
                                                   &(plan->pcur), mtr);

        /* If the cursor is traveling upwards, and relative_position is

        (1) BTR_PCUR_BEFORE: this is not allowed, as we did not have a lock
        yet on the successor of the page infimum;
        (2) BTR_PCUR_AFTER: btr_pcur_restore_position placed the cursor on the
        first record GREATER than the predecessor of a page supremum; we have
        not yet processed the cursor record: no need to move the cursor to the
        next record;
        (3) BTR_PCUR_ON: btr_pcur_restore_position placed the cursor on the
        last record LESS or EQUAL to the old stored user record; (a) if
        equal_position is FALSE, this means that the cursor is now on a record
        less than the old user record, and we must move to the next record;
        (b) if equal_position is TRUE, then if
        plan->stored_cursor_rec_processed is TRUE, we must move to the next
        record, else there is no need to move the cursor. */

        if (plan->asc) {
                if (relative_position == BTR_PCUR_ON) {

                        if (equal_position) {

                                return(plan->stored_cursor_rec_processed);
                        }

                        return(TRUE);
                }

                ut_ad(relative_position == BTR_PCUR_AFTER
                      || relative_position == BTR_PCUR_AFTER_LAST_IN_TREE);

                return(FALSE);
        }

        /* If the cursor is traveling downwards, and relative_position is

        (1) BTR_PCUR_BEFORE: btr_pcur_restore_position placed the cursor on
        the last record LESS than the successor of a page infimum; we have not
        processed the cursor record: no need to move the cursor;
        (2) BTR_PCUR_AFTER: btr_pcur_restore_position placed the cursor on the
        first record GREATER than the predecessor of a page supremum; we have
        processed the cursor record: we should move the cursor to the previous
        record;
        (3) BTR_PCUR_ON: btr_pcur_restore_position placed the cursor on the
        last record LESS or EQUAL to the old stored user record; (a) if
        equal_position is FALSE, this means that the cursor is now on a record
        less than the old user record, and we need not move to the previous
        record; (b) if equal_position is TRUE, then if
        plan->stored_cursor_rec_processed is TRUE, we must move to the previous
        record, else there is no need to move the cursor. */

        if (relative_position == BTR_PCUR_BEFORE
            || relative_position == BTR_PCUR_BEFORE_FIRST_IN_TREE) {

                return(FALSE);
        }

        if (relative_position == BTR_PCUR_ON) {

                if (equal_position) {

                        return(plan->stored_cursor_rec_processed);
                }

                return(FALSE);
        }

        ut_ad(relative_position == BTR_PCUR_AFTER
              || relative_position == BTR_PCUR_AFTER_LAST_IN_TREE);

        return(TRUE);
}

/*********************************************************************//**
Resets a plan cursor to a closed state. */
UNIV_INLINE
void
plan_reset_cursor(
/*==============*/
        plan_t* plan)   /*!< in: plan */
{
        plan->pcur_is_open = FALSE;
        plan->cursor_at_end = FALSE;
        plan->n_rows_fetched = 0;
        plan->n_rows_prefetched = 0;
}

/*********************************************************************//**
Tries to do a shortcut to fetch a clustered index record with a unique key,
using the hash index if possible (not always).
@return SEL_FOUND, SEL_EXHAUSTED, SEL_RETRY */
static
ulint
row_sel_try_search_shortcut(
/*========================*/
        sel_node_t*     node,   /*!< in: select node for a consistent read */
        plan_t*         plan,   /*!< in: plan for a unique search in clustered
                                index */
        mtr_t*          mtr)    /*!< in: mtr */
{
        dict_index_t*   index;
        rec_t*          rec;
        mem_heap_t*     heap            = NULL;
        ulint           offsets_[REC_OFFS_NORMAL_SIZE];
        ulint*          offsets         = offsets_;
        ulint           ret;
        rec_offs_init(offsets_);

        index = plan->index;

        ut_ad(node->read_view);
        ut_ad(plan->unique_search);
        ut_ad(!plan->must_get_clust);
#ifdef UNIV_SYNC_DEBUG
        ut_ad(rw_lock_own(&btr_search_latch, RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */

        row_sel_open_pcur(plan, TRUE, mtr);

        rec = btr_pcur_get_rec(&(plan->pcur));

        if (!page_rec_is_user_rec(rec)) {

                return(SEL_RETRY);
        }

        ut_ad(plan->mode == PAGE_CUR_GE);

        /* As the cursor is now placed on a user record after a search with
        the mode PAGE_CUR_GE, the up_match field in the cursor tells how many
        fields in the user record matched to the search tuple */

        if (btr_pcur_get_up_match(&(plan->pcur)) < plan->n_exact_match) {

                return(SEL_EXHAUSTED);
        }

        /* This is a non-locking consistent read: if necessary, fetch
        a previous version of the record */

        offsets = rec_get_offsets(rec, index, offsets, ULINT_UNDEFINED, &heap);

        if (dict_index_is_clust(index)) {
                if (!lock_clust_rec_cons_read_sees(rec, index, offsets,
                                                   node->read_view)) {
                        ret = SEL_RETRY;
                        goto func_exit;
                }
        } else if (!lock_sec_rec_cons_read_sees(rec, node->read_view)) {

                ret = SEL_RETRY;
                goto func_exit;
        }

        /* Test the deleted flag. */

        if (rec_get_deleted_flag(rec, dict_table_is_comp(plan->table))) {

                ret = SEL_EXHAUSTED;
                goto func_exit;
        }

        /* Fetch the columns needed in test conditions.  The index
        record is protected by a page latch that was acquired when
        plan->pcur was positioned.  The latch will not be released
        until mtr_commit(mtr). */

        row_sel_fetch_columns(index, rec, offsets,
                              UT_LIST_GET_FIRST(plan->columns));

        /* Test the rest of search conditions */

        if (!row_sel_test_other_conds(plan)) {

                ret = SEL_EXHAUSTED;
                goto func_exit;
        }

        ut_ad(plan->pcur.latch_mode == BTR_SEARCH_LEAF);

        plan->n_rows_fetched++;
        ret = SEL_FOUND;
func_exit:
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }
        return(ret);
}

/*********************************************************************//**
Performs a select step.
@return DB_SUCCESS or error code */
static
ulint
row_sel(
/*====*/
        sel_node_t*     node,   /*!< in: select node */
        que_thr_t*      thr)    /*!< in: query thread */
{
        dict_index_t*   index;
        plan_t*         plan;
        mtr_t           mtr;
        ibool           moved;
        rec_t*          rec;
        rec_t*          old_vers;
        rec_t*          clust_rec;
        ibool           search_latch_locked;
        ibool           consistent_read;

        /* The following flag becomes TRUE when we are doing a
        consistent read from a non-clustered index and we must look
        at the clustered index to find out the previous delete mark
        state of the non-clustered record: */

        ibool           cons_read_requires_clust_rec    = FALSE;
        ulint           cost_counter                    = 0;
        ibool           cursor_just_opened;
        ibool           must_go_to_next;
        ibool           mtr_has_extra_clust_latch       = FALSE;
        /* TRUE if the search was made using
        a non-clustered index, and we had to
        access the clustered record: now &mtr
        contains a clustered index latch, and
        &mtr must be committed before we move
        to the next non-clustered record */
        ulint           found_flag;
        ulint           err;
        mem_heap_t*     heap                            = NULL;
        ulint           offsets_[REC_OFFS_NORMAL_SIZE];
        ulint*          offsets                         = offsets_;
        rec_offs_init(offsets_);

        ut_ad(thr->run_node == node);

        search_latch_locked = FALSE;

        if (node->read_view) {
                /* In consistent reads, we try to do with the hash index and
                not to use the buffer page get. This is to reduce memory bus
                load resulting from semaphore operations. The search latch
                will be s-locked when we access an index with a unique search
                condition, but not locked when we access an index with a
                less selective search condition. */

                consistent_read = TRUE;
        } else {
                consistent_read = FALSE;
        }

table_loop:
        /* TABLE LOOP
        ----------
        This is the outer major loop in calculating a join. We come here when
        node->fetch_table changes, and after adding a row to aggregate totals
        and, of course, when this function is called. */

        ut_ad(mtr_has_extra_clust_latch == FALSE);

        plan = sel_node_get_nth_plan(node, node->fetch_table);
        index = plan->index;

        if (plan->n_rows_prefetched > 0) {
                sel_pop_prefetched_row(plan);

                goto next_table_no_mtr;
        }

        if (plan->cursor_at_end) {
                /* The cursor has already reached the result set end: no more
                rows to process for this table cursor, as also the prefetch
                stack was empty */

                ut_ad(plan->pcur_is_open);

                goto table_exhausted_no_mtr;
        }

        /* Open a cursor to index, or restore an open cursor position */

        mtr_start(&mtr);

        if (consistent_read && plan->unique_search && !plan->pcur_is_open
            && !plan->must_get_clust
            && !plan->table->big_rows) {
                if (!search_latch_locked) {
                        rw_lock_s_lock(&btr_search_latch);

                        search_latch_locked = TRUE;
                } else if (rw_lock_get_writer(&btr_search_latch) == RW_LOCK_WAIT_EX) {

                        /* There is an x-latch request waiting: release the
                        s-latch for a moment; as an s-latch here is often
                        kept for some 10 searches before being released,
                        a waiting x-latch request would block other threads
                        from acquiring an s-latch for a long time, lowering
                        performance significantly in multiprocessors. */

                        rw_lock_s_unlock(&btr_search_latch);
                        rw_lock_s_lock(&btr_search_latch);
                }

                found_flag = row_sel_try_search_shortcut(node, plan, &mtr);

                if (found_flag == SEL_FOUND) {

                        goto next_table;

                } else if (found_flag == SEL_EXHAUSTED) {

                        goto table_exhausted;
                }

                ut_ad(found_flag == SEL_RETRY);

                plan_reset_cursor(plan);

                mtr_commit(&mtr);
                mtr_start(&mtr);
        }

        if (search_latch_locked) {
                rw_lock_s_unlock(&btr_search_latch);

                search_latch_locked = FALSE;
        }

        if (!plan->pcur_is_open) {
                /* Evaluate the expressions to build the search tuple and
                open the cursor */

                row_sel_open_pcur(plan, search_latch_locked, &mtr);

                cursor_just_opened = TRUE;

                /* A new search was made: increment the cost counter */
                cost_counter++;
        } else {
                /* Restore pcur position to the index */

                must_go_to_next = row_sel_restore_pcur_pos(plan, &mtr);

                cursor_just_opened = FALSE;

                if (must_go_to_next) {
                        /* We have already processed the cursor record: move
                        to the next */

                        goto next_rec;
                }
        }

rec_loop:
        /* RECORD LOOP
        -----------
        In this loop we use pcur and try to fetch a qualifying row, and
        also fill the prefetch buffer for this table if n_rows_fetched has
        exceeded a threshold. While we are inside this loop, the following
        holds:
        (1) &mtr is started,
        (2) pcur is positioned and open.

        NOTE that if cursor_just_opened is TRUE here, it means that we came
        to this point right after row_sel_open_pcur. */

        ut_ad(mtr_has_extra_clust_latch == FALSE);

        rec = btr_pcur_get_rec(&(plan->pcur));

        /* PHASE 1: Set a lock if specified */

        if (!node->asc && cursor_just_opened
            && !page_rec_is_supremum(rec)) {

                /* When we open a cursor for a descending search, we must set
                a next-key lock on the successor record: otherwise it would
                be possible to insert new records next to the cursor position,
                and it might be that these new records should appear in the
                search result set, resulting in the phantom problem. */

                if (!consistent_read) {

                        /* If innodb_locks_unsafe_for_binlog option is used
                        or this session is using READ COMMITTED isolation
                        level, we lock only the record, i.e., next-key
                        locking is not used. */

                        rec_t*  next_rec = page_rec_get_next(rec);
                        ulint   lock_type;
                        trx_t*  trx;

                        trx = thr_get_trx(thr);

                        offsets = rec_get_offsets(next_rec, index, offsets,
                                                  ULINT_UNDEFINED, &heap);

                        if (srv_locks_unsafe_for_binlog
                            || trx->isolation_level
                            <= TRX_ISO_READ_COMMITTED) {

                                if (page_rec_is_supremum(next_rec)) {

                                        goto skip_lock;
                                }

                                lock_type = LOCK_REC_NOT_GAP;
                        } else {
                                lock_type = LOCK_ORDINARY;
                        }

                        err = sel_set_rec_lock(btr_pcur_get_block(&plan->pcur),
                                               next_rec, index, offsets,
                                               node->row_lock_mode,
                                               lock_type, thr);

                        switch (err) {
                        case DB_SUCCESS_LOCKED_REC:
                                err = DB_SUCCESS;
                        case DB_SUCCESS:
                                break;
                        default:
                                /* Note that in this case we will store in pcur
                                the PREDECESSOR of the record we are waiting
                                the lock for */
                                goto lock_wait_or_error;
                        }
                }
        }

skip_lock:
        if (page_rec_is_infimum(rec)) {

                /* The infimum record on a page cannot be in the result set,
                and neither can a record lock be placed on it: we skip such
                a record. We also increment the cost counter as we may have
                processed yet another page of index. */

                cost_counter++;

                goto next_rec;
        }

        if (!consistent_read) {
                /* Try to place a lock on the index record */

                /* If innodb_locks_unsafe_for_binlog option is used
                or this session is using READ COMMITTED isolation level,
                we lock only the record, i.e., next-key locking is
                not used. */

                ulint   lock_type;
                trx_t*  trx;

                offsets = rec_get_offsets(rec, index, offsets,
                                          ULINT_UNDEFINED, &heap);

                trx = thr_get_trx(thr);

                if (srv_locks_unsafe_for_binlog
                    || trx->isolation_level <= TRX_ISO_READ_COMMITTED) {

                        if (page_rec_is_supremum(rec)) {

                                goto next_rec;
                        }

                        lock_type = LOCK_REC_NOT_GAP;
                } else {
                        lock_type = LOCK_ORDINARY;
                }

                err = sel_set_rec_lock(btr_pcur_get_block(&plan->pcur),
                                       rec, index, offsets,
                                       node->row_lock_mode, lock_type, thr);

                switch (err) {
                case DB_SUCCESS_LOCKED_REC:
                        err = DB_SUCCESS;
                case DB_SUCCESS:
                        break;
                default:
                        goto lock_wait_or_error;
                }
        }

        if (page_rec_is_supremum(rec)) {

                /* A page supremum record cannot be in the result set: skip
                it now when we have placed a possible lock on it */

                goto next_rec;
        }

        ut_ad(page_rec_is_user_rec(rec));

        if (cost_counter > SEL_COST_LIMIT) {

                /* Now that we have placed the necessary locks, we can stop
                for a while and store the cursor position; NOTE that if we
                would store the cursor position BEFORE placing a record lock,
                it might happen that the cursor would jump over some records
                that another transaction could meanwhile insert adjacent to
                the cursor: this would result in the phantom problem. */

                goto stop_for_a_while;
        }

        /* PHASE 2: Check a mixed index mix id if needed */

        if (plan->unique_search && cursor_just_opened) {

                ut_ad(plan->mode == PAGE_CUR_GE);

                /* As the cursor is now placed on a user record after a search
                with the mode PAGE_CUR_GE, the up_match field in the cursor
                tells how many fields in the user record matched to the search
                tuple */

                if (btr_pcur_get_up_match(&(plan->pcur))
                    < plan->n_exact_match) {
                        goto table_exhausted;
                }

                /* Ok, no need to test end_conds or mix id */

        }

        /* We are ready to look at a possible new index entry in the result
        set: the cursor is now placed on a user record */

        /* PHASE 3: Get previous version in a consistent read */

        cons_read_requires_clust_rec = FALSE;
        offsets = rec_get_offsets(rec, index, offsets, ULINT_UNDEFINED, &heap);

        if (consistent_read) {
                /* This is a non-locking consistent read: if necessary, fetch
                a previous version of the record */

                if (dict_index_is_clust(index)) {

                        if (!lock_clust_rec_cons_read_sees(rec, index, offsets,
                                                           node->read_view)) {

                                err = row_sel_build_prev_vers(
                                        node->read_view, index, rec,
                                        &offsets, &heap, &plan->old_vers_heap,
                                        &old_vers, &mtr);

                                if (err != DB_SUCCESS) {

                                        goto lock_wait_or_error;
                                }

                                if (old_vers == NULL) {
                                        /* The record does not exist
                                        in our read view. Skip it, but
                                        first attempt to determine
                                        whether the index segment we
                                        are searching through has been
                                        exhausted. */

                                        offsets = rec_get_offsets(
                                                rec, index, offsets,
                                                ULINT_UNDEFINED, &heap);

                                        /* Fetch the columns needed in
                                        test conditions. The clustered
                                        index record is protected by a
                                        page latch that was acquired
                                        by row_sel_open_pcur() or
                                        row_sel_restore_pcur_pos().
                                        The latch will not be released
                                        until mtr_commit(mtr). */

                                        row_sel_fetch_columns(
                                                index, rec, offsets,
                                                UT_LIST_GET_FIRST(
                                                        plan->columns));

                                        if (!row_sel_test_end_conds(plan)) {

                                                goto table_exhausted;
                                        }

                                        goto next_rec;
                                }

                                rec = old_vers;
                        }
                } else if (!lock_sec_rec_cons_read_sees(rec,
                                                        node->read_view)) {
                        cons_read_requires_clust_rec = TRUE;
                }
        }

        /* PHASE 4: Test search end conditions and deleted flag */

        /* Fetch the columns needed in test conditions.  The record is
        protected by a page latch that was acquired by
        row_sel_open_pcur() or row_sel_restore_pcur_pos().  The latch
        will not be released until mtr_commit(mtr). */

        row_sel_fetch_columns(index, rec, offsets,
                              UT_LIST_GET_FIRST(plan->columns));

        /* Test the selection end conditions: these can only contain columns
        which already are found in the index, even though the index might be
        non-clustered */

        if (plan->unique_search && cursor_just_opened) {

                /* No test necessary: the test was already made above */

        } else if (!row_sel_test_end_conds(plan)) {

                goto table_exhausted;
        }

        if (rec_get_deleted_flag(rec, dict_table_is_comp(plan->table))
            && !cons_read_requires_clust_rec) {

                /* The record is delete marked: we can skip it if this is
                not a consistent read which might see an earlier version
                of a non-clustered index record */

                if (plan->unique_search) {

                        goto table_exhausted;
                }

                goto next_rec;
        }

        /* PHASE 5: Get the clustered index record, if needed and if we did
        not do the search using the clustered index */

        if (plan->must_get_clust || cons_read_requires_clust_rec) {

                /* It was a non-clustered index and we must fetch also the
                clustered index record */

                err = row_sel_get_clust_rec(node, plan, rec, thr, &clust_rec,
                                            &mtr);
                mtr_has_extra_clust_latch = TRUE;

                if (err != DB_SUCCESS) {

                        goto lock_wait_or_error;
                }

                /* Retrieving the clustered record required a search:
                increment the cost counter */

                cost_counter++;

                if (clust_rec == NULL) {
                        /* The record did not exist in the read view */
                        ut_ad(consistent_read);

                        goto next_rec;
                }

                if (rec_get_deleted_flag(clust_rec,
                                         dict_table_is_comp(plan->table))) {

                        /* The record is delete marked: we can skip it */

                        goto next_rec;
                }

                if (node->can_get_updated) {

                        btr_pcur_store_position(&(plan->clust_pcur), &mtr);
                }
        }

        /* PHASE 6: Test the rest of search conditions */

        if (!row_sel_test_other_conds(plan)) {

                if (plan->unique_search) {

                        goto table_exhausted;
                }

                goto next_rec;
        }

        /* PHASE 7: We found a new qualifying row for the current table; push
        the row if prefetch is on, or move to the next table in the join */

        plan->n_rows_fetched++;

        ut_ad(plan->pcur.latch_mode == BTR_SEARCH_LEAF);

        if ((plan->n_rows_fetched <= SEL_PREFETCH_LIMIT)
            || plan->unique_search || plan->no_prefetch
            || plan->table->big_rows) {

                /* No prefetch in operation: go to the next table */

                goto next_table;
        }

        sel_push_prefetched_row(plan);

        if (plan->n_rows_prefetched == SEL_MAX_N_PREFETCH) {

                /* The prefetch buffer is now full */

                sel_pop_prefetched_row(plan);

                goto next_table;
        }

next_rec:
        ut_ad(!search_latch_locked);

        if (mtr_has_extra_clust_latch) {

                /* We must commit &mtr if we are moving to the next
                non-clustered index record, because we could break the
                latching order if we would access a different clustered
                index page right away without releasing the previous. */

                goto commit_mtr_for_a_while;
        }

        if (node->asc) {
                moved = btr_pcur_move_to_next(&(plan->pcur), &mtr);
        } else {
                moved = btr_pcur_move_to_prev(&(plan->pcur), &mtr);
        }

        if (!moved) {

                goto table_exhausted;
        }

        cursor_just_opened = FALSE;

        /* END OF RECORD LOOP
        ------------------ */
        goto rec_loop;

next_table:
        /* We found a record which satisfies the conditions: we can move to
        the next table or return a row in the result set */

        ut_ad(btr_pcur_is_on_user_rec(&plan->pcur));

        if (plan->unique_search && !node->can_get_updated) {

                plan->cursor_at_end = TRUE;
        } else {
                ut_ad(!search_latch_locked);

                plan->stored_cursor_rec_processed = TRUE;

                btr_pcur_store_position(&(plan->pcur), &mtr);
        }

        mtr_commit(&mtr);

        mtr_has_extra_clust_latch = FALSE;

next_table_no_mtr:
        /* If we use 'goto' to this label, it means that the row was popped
        from the prefetched rows stack, and &mtr is already committed */

        if (node->fetch_table + 1 == node->n_tables) {

                sel_eval_select_list(node);

                if (node->is_aggregate) {

                        goto table_loop;
                }

                sel_assign_into_var_values(node->into_list, node);

                thr->run_node = que_node_get_parent(node);

                err = DB_SUCCESS;
                goto func_exit;
        }

        node->fetch_table++;

        /* When we move to the next table, we first reset the plan cursor:
        we do not care about resetting it when we backtrack from a table */

        plan_reset_cursor(sel_node_get_nth_plan(node, node->fetch_table));

        goto table_loop;

table_exhausted:
        /* The table cursor pcur reached the result set end: backtrack to the
        previous table in the join if we do not have cached prefetched rows */

        plan->cursor_at_end = TRUE;

        mtr_commit(&mtr);

        mtr_has_extra_clust_latch = FALSE;

        if (plan->n_rows_prefetched > 0) {
                /* The table became exhausted during a prefetch */

                sel_pop_prefetched_row(plan);

                goto next_table_no_mtr;
        }

table_exhausted_no_mtr:
        if (node->fetch_table == 0) {
                err = DB_SUCCESS;

                if (node->is_aggregate && !node->aggregate_already_fetched) {

                        node->aggregate_already_fetched = TRUE;

                        sel_assign_into_var_values(node->into_list, node);

                        thr->run_node = que_node_get_parent(node);
                } else {
                        node->state = SEL_NODE_NO_MORE_ROWS;

                        thr->run_node = que_node_get_parent(node);
                }

                goto func_exit;
        }

        node->fetch_table--;

        goto table_loop;

stop_for_a_while:
        /* Return control for a while to que_run_threads, so that runaway
        queries can be canceled. NOTE that when we come here, we must, in a
        locking read, have placed the necessary (possibly waiting request)
        record lock on the cursor record or its successor: when we reposition
        the cursor, this record lock guarantees that nobody can meanwhile have
        inserted new records which should have appeared in the result set,
        which would result in the phantom problem. */

        ut_ad(!search_latch_locked);

        plan->stored_cursor_rec_processed = FALSE;
        btr_pcur_store_position(&(plan->pcur), &mtr);

        mtr_commit(&mtr);

#ifdef UNIV_SYNC_DEBUG
        ut_ad(sync_thread_levels_empty_gen(TRUE));
#endif /* UNIV_SYNC_DEBUG */
        err = DB_SUCCESS;
        goto func_exit;

commit_mtr_for_a_while:
        /* Stores the cursor position and commits &mtr; this is used if
        &mtr may contain latches which would break the latching order if
        &mtr would not be committed and the latches released. */

        plan->stored_cursor_rec_processed = TRUE;

        ut_ad(!search_latch_locked);
        btr_pcur_store_position(&(plan->pcur), &mtr);

        mtr_commit(&mtr);

        mtr_has_extra_clust_latch = FALSE;

#ifdef UNIV_SYNC_DEBUG
        ut_ad(sync_thread_levels_empty_gen(TRUE));
#endif /* UNIV_SYNC_DEBUG */

        goto table_loop;

lock_wait_or_error:
        /* See the note at stop_for_a_while: the same holds for this case */

        ut_ad(!btr_pcur_is_before_first_on_page(&plan->pcur) || !node->asc);
        ut_ad(!search_latch_locked);

        plan->stored_cursor_rec_processed = FALSE;
        btr_pcur_store_position(&(plan->pcur), &mtr);

        mtr_commit(&mtr);

#ifdef UNIV_SYNC_DEBUG
        ut_ad(sync_thread_levels_empty_gen(TRUE));
#endif /* UNIV_SYNC_DEBUG */

func_exit:
        if (search_latch_locked) {
                rw_lock_s_unlock(&btr_search_latch);
        }
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }
        return(err);
}

/**********************************************************************//**
Performs a select step. This is a high-level function used in SQL execution
graphs.
@return query thread to run next or NULL */
UNIV_INTERN
que_thr_t*
row_sel_step(
/*=========*/
        que_thr_t*      thr)    /*!< in: query thread */
{
        ulint           i_lock_mode;
        sym_node_t*     table_node;
        sel_node_t*     node;
        ulint           err;

        ut_ad(thr);

        node = thr->run_node;

        ut_ad(que_node_get_type(node) == QUE_NODE_SELECT);

        /* If this is a new time this node is executed (or when execution
        resumes after wait for a table intention lock), set intention locks
        on the tables, or assign a read view */

        if (node->into_list && (thr->prev_node == que_node_get_parent(node))) {

                node->state = SEL_NODE_OPEN;
        }

        if (node->state == SEL_NODE_OPEN) {

                /* It may be that the current session has not yet started
                its transaction, or it has been committed: */

                trx_start_if_not_started(thr_get_trx(thr));

                plan_reset_cursor(sel_node_get_nth_plan(node, 0));

                if (node->consistent_read) {
                        /* Assign a read view for the query */
                        node->read_view = trx_assign_read_view(
                                thr_get_trx(thr));
                } else {
                        if (node->set_x_locks) {
                                i_lock_mode = LOCK_IX;
                        } else {
                                i_lock_mode = LOCK_IS;
                        }

                        table_node = node->table_list;

                        while (table_node) {
                                err = lock_table(0, table_node->table,
                                                 i_lock_mode, thr);
                                if (err != DB_SUCCESS) {
                                        thr_get_trx(thr)->error_state = err;

                                        return(NULL);
                                }

                                table_node = que_node_get_next(table_node);
                        }
                }

                /* If this is an explicit cursor, copy stored procedure
                variable values, so that the values cannot change between
                fetches (currently, we copy them also for non-explicit
                cursors) */

                if (node->explicit_cursor
                    && UT_LIST_GET_FIRST(node->copy_variables)) {

                        row_sel_copy_input_variable_vals(node);
                }

                node->state = SEL_NODE_FETCH;
                node->fetch_table = 0;

                if (node->is_aggregate) {
                        /* Reset the aggregate total values */
                        sel_reset_aggregate_vals(node);
                }
        }

        err = row_sel(node, thr);

        /* NOTE! if queries are parallelized, the following assignment may
        have problems; the assignment should be made only if thr is the
        only top-level thr in the graph: */

        thr->graph->last_sel_node = node;

        if (err != DB_SUCCESS) {
                thr_get_trx(thr)->error_state = err;

                return(NULL);
        }

        return(thr);
}

/**********************************************************************//**
Performs a fetch for a cursor.
@return query thread to run next or NULL */
UNIV_INTERN
que_thr_t*
fetch_step(
/*=======*/
        que_thr_t*      thr)    /*!< in: query thread */
{
        sel_node_t*     sel_node;
        fetch_node_t*   node;

        ut_ad(thr);

        node = thr->run_node;
        sel_node = node->cursor_def;

        ut_ad(que_node_get_type(node) == QUE_NODE_FETCH);

        if (thr->prev_node != que_node_get_parent(node)) {

                if (sel_node->state != SEL_NODE_NO_MORE_ROWS) {

                        if (node->into_list) {
                                sel_assign_into_var_values(node->into_list,
                                                           sel_node);
                        } else {
                                void* ret = (*node->func->func)(
                                        sel_node, node->func->arg);

                                if (!ret) {
                                        sel_node->state
                                                = SEL_NODE_NO_MORE_ROWS;
                                }
                        }
                }

                thr->run_node = que_node_get_parent(node);

                return(thr);
        }

        /* Make the fetch node the parent of the cursor definition for
        the time of the fetch, so that execution knows to return to this
        fetch node after a row has been selected or we know that there is
        no row left */

        sel_node->common.parent = node;

        if (sel_node->state == SEL_NODE_CLOSED) {
                fprintf(stderr,
                        "InnoDB: Error: fetch called on a closed cursor\n");

                thr_get_trx(thr)->error_state = DB_ERROR;

                return(NULL);
        }

        thr->run_node = sel_node;

        return(thr);
}

/****************************************************************//**
Sample callback function for fetch that prints each row.
@return always returns non-NULL */
UNIV_INTERN
void*
row_fetch_print(
/*============*/
        void*   row,            /*!< in:  sel_node_t* */
        void*   user_arg)       /*!< in:  not used */
{
        sel_node_t*     node = row;
        que_node_t*     exp;
        ulint           i = 0;

        UT_NOT_USED(user_arg);

        fprintf(stderr, "row_fetch_print: row %p\n", row);

        exp = node->select_list;

        while (exp) {
                dfield_t*       dfield = que_node_get_val(exp);
                const dtype_t*  type = dfield_get_type(dfield);

                fprintf(stderr, " column %lu:\n", (ulong)i);

                dtype_print(type);
                putc('\n', stderr);

                if (dfield_get_len(dfield) != UNIV_SQL_NULL) {
                        ut_print_buf(stderr, dfield_get_data(dfield),
                                     dfield_get_len(dfield));
                        putc('\n', stderr);
                } else {
                        fputs(" <NULL>;\n", stderr);
                }

                exp = que_node_get_next(exp);
                i++;
        }

        return((void*)42);
}

/***********************************************************//**
Prints a row in a select result.
@return query thread to run next or NULL */
UNIV_INTERN
que_thr_t*
row_printf_step(
/*============*/
        que_thr_t*      thr)    /*!< in: query thread */
{
        row_printf_node_t*      node;
        sel_node_t*             sel_node;
        que_node_t*             arg;

        ut_ad(thr);

        node = thr->run_node;

        sel_node = node->sel_node;

        ut_ad(que_node_get_type(node) == QUE_NODE_ROW_PRINTF);

        if (thr->prev_node == que_node_get_parent(node)) {

                /* Reset the cursor */
                sel_node->state = SEL_NODE_OPEN;

                /* Fetch next row to print */

                thr->run_node = sel_node;

                return(thr);
        }

        if (sel_node->state != SEL_NODE_FETCH) {

                ut_ad(sel_node->state == SEL_NODE_NO_MORE_ROWS);

                /* No more rows to print */

                thr->run_node = que_node_get_parent(node);

                return(thr);
        }

        arg = sel_node->select_list;

        while (arg) {
                dfield_print_also_hex(que_node_get_val(arg));

                fputs(" ::: ", stderr);

                arg = que_node_get_next(arg);
        }

        putc('\n', stderr);

        /* Fetch next row to print */

        thr->run_node = sel_node;

        return(thr);
}

/****************************************************************//**
Converts a key value stored in MySQL format to an Innobase dtuple. The last
field of the key value may be just a prefix of a fixed length field: hence
the parameter key_len. But currently we do not allow search keys where the
last field is only a prefix of the full key field len and print a warning if
such appears. A counterpart of this function is
ha_innobase::store_key_val_for_row() in ha_innodb.cc. */
UNIV_INTERN
void
row_sel_convert_mysql_key_to_innobase(
/*==================================*/
        dtuple_t*       tuple,          /*!< in/out: tuple where to build;
                                        NOTE: we assume that the type info
                                        in the tuple is already according
                                        to index! */
        byte*           buf,            /*!< in: buffer to use in field
                                        conversions */
        ulint           buf_len,        /*!< in: buffer length */
        dict_index_t*   index,          /*!< in: index of the key value */
        const byte*     key_ptr,        /*!< in: MySQL key value */
        ulint           key_len,        /*!< in: MySQL key value length */
        trx_t*          trx)            /*!< in: transaction */
{
        byte*           original_buf    = buf;
        const byte*     original_key_ptr = key_ptr;
        dict_field_t*   field;
        dfield_t*       dfield;
        ulint           data_offset;
        ulint           data_len;
        ulint           data_field_len;
        ibool           is_null;
        const byte*     key_end;
        ulint           n_fields = 0;

        /* For documentation of the key value storage format in MySQL, see
        ha_innobase::store_key_val_for_row() in ha_innodb.cc. */

        key_end = key_ptr + key_len;

        /* Permit us to access any field in the tuple (ULINT_MAX): */

        dtuple_set_n_fields(tuple, ULINT_MAX);

        dfield = dtuple_get_nth_field(tuple, 0);
        field = dict_index_get_nth_field(index, 0);

        if (UNIV_UNLIKELY(dfield_get_type(dfield)->mtype == DATA_SYS)) {
                /* A special case: we are looking for a position in the
                generated clustered index which InnoDB automatically added
                to a table with no primary key: the first and the only
                ordering column is ROW_ID which InnoDB stored to the key_ptr
                buffer. */

                ut_a(key_len == DATA_ROW_ID_LEN);

                dfield_set_data(dfield, key_ptr, DATA_ROW_ID_LEN);

                dtuple_set_n_fields(tuple, 1);

                return;
        }

        while (key_ptr < key_end) {

                ulint   type = dfield_get_type(dfield)->mtype;
                ut_a(field->col->mtype == type);

                data_offset = 0;
                is_null = FALSE;

                if (!(dfield_get_type(dfield)->prtype & DATA_NOT_NULL)) {
                        /* The first byte in the field tells if this is
                        an SQL NULL value */

                        data_offset = 1;

                        if (*key_ptr != 0) {
                                dfield_set_null(dfield);

                                is_null = TRUE;
                        }
                }

                /* Calculate data length and data field total length */

                if (type == DATA_BLOB) {
                        /* The key field is a column prefix of a BLOB or
                        TEXT */

                        ut_a(field->prefix_len > 0);

                        /* MySQL stores the actual data length to the first 2
                        bytes after the optional SQL NULL marker byte. The
                        storage format is little-endian, that is, the most
                        significant byte at a higher address. In UTF-8, MySQL
                        seems to reserve field->prefix_len bytes for
                        storing this field in the key value buffer, even
                        though the actual value only takes data_len bytes
                        from the start. */

                        data_len = key_ptr[data_offset]
                                + 256 * key_ptr[data_offset + 1];
                        data_field_len = data_offset + 2 + field->prefix_len;

                        data_offset += 2;

                        /* Now that we know the length, we store the column
                        value like it would be a fixed char field */

                } else if (field->prefix_len > 0) {
                        /* Looks like MySQL pads unused end bytes in the
                        prefix with space. Therefore, also in UTF-8, it is ok
                        to compare with a prefix containing full prefix_len
                        bytes, and no need to take at most prefix_len / 3
                        UTF-8 characters from the start.
                        If the prefix is used as the upper end of a LIKE
                        'abc%' query, then MySQL pads the end with chars
                        0xff. TODO: in that case does it any harm to compare
                        with the full prefix_len bytes. How do characters
                        0xff in UTF-8 behave? */

                        data_len = field->prefix_len;
                        data_field_len = data_offset + data_len;
                } else {
                        data_len = dfield_get_type(dfield)->len;
                        data_field_len = data_offset + data_len;
                }

                if (UNIV_UNLIKELY
                    (dtype_get_mysql_type(dfield_get_type(dfield))
                     == DATA_MYSQL_TRUE_VARCHAR)
                    && UNIV_LIKELY(type != DATA_INT)) {
                        /* In a MySQL key value format, a true VARCHAR is
                        always preceded by 2 bytes of a length field.
                        dfield_get_type(dfield)->len returns the maximum
                        'payload' len in bytes. That does not include the
                        2 bytes that tell the actual data length.

                        We added the check != DATA_INT to make sure we do
                        not treat MySQL ENUM or SET as a true VARCHAR! */

                        data_len += 2;
                        data_field_len += 2;
                }

                /* Storing may use at most data_len bytes of buf */

                if (UNIV_LIKELY(!is_null)) {
                        row_mysql_store_col_in_innobase_format(
                                dfield, buf,
                                FALSE, /* MySQL key value format col */
                                key_ptr + data_offset, data_len,
                                dict_table_is_comp(index->table));
                        buf += data_len;
                }

                key_ptr += data_field_len;

                if (UNIV_UNLIKELY(key_ptr > key_end)) {
                        /* The last field in key was not a complete key field
                        but a prefix of it.

                        Print a warning about this! HA_READ_PREFIX_LAST does
                        not currently work in InnoDB with partial-field key
                        value prefixes. Since MySQL currently uses a padding
                        trick to calculate LIKE 'abc%' type queries there
                        should never be partial-field prefixes in searches. */

                        ut_print_timestamp(stderr);

                        fputs("  InnoDB: Warning: using a partial-field"
                              " key prefix in search.\n"
                              "InnoDB: ", stderr);
                        dict_index_name_print(stderr, trx, index);
                        fprintf(stderr, ". Last data field length %lu bytes,\n"
                                "InnoDB: key ptr now exceeds"
                                " key end by %lu bytes.\n"
                                "InnoDB: Key value in the MySQL format:\n",
                                (ulong) data_field_len,
                                (ulong) (key_ptr - key_end));
                        fflush(stderr);
                        ut_print_buf(stderr, original_key_ptr, key_len);
                        putc('\n', stderr);

                        if (!is_null) {
                                ulint   len = dfield_get_len(dfield);
                                dfield_set_len(dfield, len
                                               - (ulint) (key_ptr - key_end));
                        }
                }

                n_fields++;
                field++;
                dfield++;
        }

        ut_a(buf <= original_buf + buf_len);

        /* We set the length of tuple to n_fields: we assume that the memory
        area allocated for it is big enough (usually bigger than n_fields). */

        dtuple_set_n_fields(tuple, n_fields);
}

/**************************************************************//**
Stores the row id to the prebuilt struct. */
static
void
row_sel_store_row_id_to_prebuilt(
/*=============================*/
        row_prebuilt_t*         prebuilt,       /*!< in/out: prebuilt */
        const rec_t*            index_rec,      /*!< in: record */
        const dict_index_t*     index,          /*!< in: index of the record */
        const ulint*            offsets)        /*!< in: rec_get_offsets
                                                (index_rec, index) */
{
        const byte*     data;
        ulint           len;

        ut_ad(rec_offs_validate(index_rec, index, offsets));

        data = rec_get_nth_field(
                index_rec, offsets,
                dict_index_get_sys_col_pos(index, DATA_ROW_ID), &len);

        if (UNIV_UNLIKELY(len != DATA_ROW_ID_LEN)) {
                fprintf(stderr,
                        "InnoDB: Error: Row id field is"
                        " wrong length %lu in ", (ulong) len);
                dict_index_name_print(stderr, prebuilt->trx, index);
                fprintf(stderr, "\n"
                        "InnoDB: Field number %lu, record:\n",
                        (ulong) dict_index_get_sys_col_pos(index,
                                                           DATA_ROW_ID));
                rec_print_new(stderr, index_rec, offsets);
                putc('\n', stderr);
                ut_error;
        }

        ut_memcpy(prebuilt->row_id, data, len);
}

/**************************************************************//**
Stores a non-SQL-NULL field in the MySQL format. The counterpart of this
function is row_mysql_store_col_in_innobase_format() in row0mysql.c. */
static
void
row_sel_field_store_in_mysql_format(
/*================================*/
        byte*           dest,   /*!< in/out: buffer where to store; NOTE
                                that BLOBs are not in themselves
                                stored here: the caller must allocate
                                and copy the BLOB into buffer before,
                                and pass the pointer to the BLOB in
                                'data' */
        const mysql_row_templ_t* templ,
                                /*!< in: MySQL column template.
                                Its following fields are referenced:
                                type, is_unsigned, mysql_col_len,
                                mbminlen, mbmaxlen */
        const byte*     data,   /*!< in: data to store */
        ulint           len)    /*!< in: length of the data */
{
        byte*   ptr;
        byte*   field_end;
        byte*   pad_ptr;

        ut_ad(len != UNIV_SQL_NULL);
        UNIV_MEM_ASSERT_RW(data, len);
        UNIV_MEM_ASSERT_W(dest, templ->mysql_col_len);
        UNIV_MEM_INVALID(dest, templ->mysql_col_len);

        switch (templ->type) {
        case DATA_INT:
                /* Convert integer data from Innobase to a little-endian
                format, sign bit restored to normal */

                ptr = dest + len;

                for (;;) {
                        ptr--;
                        *ptr = *data;
                        if (ptr == dest) {
                                break;
                        }
                        data++;
                }

                if (!templ->is_unsigned) {
                        dest[len - 1] = (byte) (dest[len - 1] ^ 128);
                }

                ut_ad(templ->mysql_col_len == len);
                break;

        case DATA_VARCHAR:
        case DATA_VARMYSQL:
        case DATA_BINARY:
                field_end = dest + templ->mysql_col_len;

                if (templ->mysql_type == DATA_MYSQL_TRUE_VARCHAR) {
                        /* This is a >= 5.0.3 type true VARCHAR. Store the
                        length of the data to the first byte or the first
                        two bytes of dest. */

                        dest = row_mysql_store_true_var_len(
                                dest, len, templ->mysql_length_bytes);
                        /* Copy the actual data. Leave the rest of the
                        buffer uninitialized. */
                        memcpy(dest, data, len);
                        break;
                }

                /* Copy the actual data */
                ut_memcpy(dest, data, len);

                /* Pad with trailing spaces. */

                pad_ptr = dest + len;

                ut_ad(templ->mbminlen <= templ->mbmaxlen);

                /* We handle UCS2 charset strings differently. */
                if (templ->mbminlen == 2) {
                        /* A space char is two bytes, 0x0020 in UCS2 */

                        if (len & 1) {
                                /* A 0x20 has been stripped from the column.
                                Pad it back. */

                                if (pad_ptr < field_end) {
                                        *pad_ptr = 0x20;
                                        pad_ptr++;
                                }
                        }

                        /* Pad the rest of the string with 0x0020 */

                        while (pad_ptr < field_end) {
                                *pad_ptr = 0x00;
                                pad_ptr++;
                                *pad_ptr = 0x20;
                                pad_ptr++;
                        }
                } else {
                        ut_ad(templ->mbminlen == 1);
                        /* space=0x20 */

                        memset(pad_ptr, 0x20, field_end - pad_ptr);
                }
                break;

        case DATA_BLOB:
                /* Store a pointer to the BLOB buffer to dest: the BLOB was
                already copied to the buffer in row_sel_store_mysql_rec */

                row_mysql_store_blob_ref(dest, templ->mysql_col_len, data,
                                         len);
                break;

        case DATA_MYSQL:
                memcpy(dest, data, len);

                ut_ad(templ->mysql_col_len >= len);
                ut_ad(templ->mbmaxlen >= templ->mbminlen);

                ut_ad(templ->mbmaxlen > templ->mbminlen
                      || templ->mysql_col_len == len);
                /* The following assertion would fail for old tables
                containing UTF-8 ENUM columns due to Bug #9526. */
                ut_ad(!templ->mbmaxlen
                      || !(templ->mysql_col_len % templ->mbmaxlen));
                ut_ad(len * templ->mbmaxlen >= templ->mysql_col_len);

                if (templ->mbminlen != templ->mbmaxlen) {
                        /* Pad with spaces. This undoes the stripping
                        done in row0mysql.ic, function
                        row_mysql_store_col_in_innobase_format(). */

                        memset(dest + len, 0x20, templ->mysql_col_len - len);
                }
                break;

        default:
#ifdef UNIV_DEBUG
        case DATA_SYS_CHILD:
        case DATA_SYS:
                /* These column types should never be shipped to MySQL. */
                ut_ad(0);

        case DATA_CHAR:
        case DATA_FIXBINARY:
        case DATA_FLOAT:
        case DATA_DOUBLE:
        case DATA_DECIMAL:
                /* Above are the valid column types for MySQL data. */
#endif /* UNIV_DEBUG */
                ut_ad(templ->mysql_col_len == len);
                memcpy(dest, data, len);
        }
}

/**************************************************************//**
Convert a row in the Innobase format to a row in the MySQL format.
Note that the template in prebuilt may advise us to copy only a few
columns to mysql_rec, other columns are left blank. All columns may not
be needed in the query.
@return TRUE on success, FALSE if not all columns could be retrieved */
static __attribute__((warn_unused_result))
ibool
row_sel_store_mysql_rec(
/*====================*/
        byte*           mysql_rec,      /*!< out: row in the MySQL format */
        row_prebuilt_t* prebuilt,       /*!< in: prebuilt struct */
        const rec_t*    rec,            /*!< in: Innobase record in the index
                                        which was described in prebuilt's
                                        template, or in the clustered index;
                                        must be protected by a page latch */
        ibool           rec_clust,      /*!< in: TRUE if rec is in the
                                        clustered index instead of
                                        prebuilt->index */
        const ulint*    offsets)        /*!< in: array returned by
                                        rec_get_offsets(rec) */
{
        mem_heap_t*     extern_field_heap       = NULL;
        mem_heap_t*     heap;
        ulint           i;

        ut_ad(prebuilt->mysql_template);
        ut_ad(prebuilt->default_rec);
        ut_ad(rec_offs_validate(rec, NULL, offsets));
        ut_ad(!rec_get_deleted_flag(rec, rec_offs_comp(offsets)));

        if (UNIV_LIKELY_NULL(prebuilt->blob_heap)) {
                mem_heap_free(prebuilt->blob_heap);
                prebuilt->blob_heap = NULL;
        }

        for (i = 0; i < prebuilt->n_template; i++) {

                const mysql_row_templ_t*templ = prebuilt->mysql_template + i;
                const byte*             data;
                ulint                   len;
                ulint                   field_no;

                field_no = rec_clust
                        ? templ->clust_rec_field_no : templ->rec_field_no;

                if (UNIV_UNLIKELY(rec_offs_nth_extern(offsets, field_no))) {

                        /* Copy an externally stored field to the temporary
                        heap */

                        ut_a(!prebuilt->trx->has_search_latch);

                        if (UNIV_UNLIKELY(templ->type == DATA_BLOB)) {
                                if (prebuilt->blob_heap == NULL) {
                                        prebuilt->blob_heap = mem_heap_create(
                                                UNIV_PAGE_SIZE);
                                }

                                heap = prebuilt->blob_heap;
                        } else {
                                extern_field_heap
                                        = mem_heap_create(UNIV_PAGE_SIZE);

                                heap = extern_field_heap;
                        }

                        /* NOTE: if we are retrieving a big BLOB, we may
                        already run out of memory in the next call, which
                        causes an assert */

                        data = btr_rec_copy_externally_stored_field(
                                rec, offsets,
                                dict_table_zip_size(prebuilt->table),
                                field_no, &len, heap);

                        if (UNIV_UNLIKELY(!data)) {
                                /* The externally stored field
                                was not written yet. This
                                record should only be seen by
                                recv_recovery_rollback_active()
                                or any TRX_ISO_READ_UNCOMMITTED
                                transactions. */

                                if (extern_field_heap) {
                                        mem_heap_free(extern_field_heap);
                                }

                                return(FALSE);
                        }

                        ut_a(len != UNIV_SQL_NULL);
                } else {
                        /* Field is stored in the row. */

                        data = rec_get_nth_field(rec, offsets, field_no, &len);

                        if (UNIV_UNLIKELY(templ->type == DATA_BLOB)
                            && len != UNIV_SQL_NULL) {

                                /* It is a BLOB field locally stored in the
                                InnoDB record: we MUST copy its contents to
                                prebuilt->blob_heap here because later code
                                assumes all BLOB values have been copied to a
                                safe place. */

                                if (prebuilt->blob_heap == NULL) {
                                        prebuilt->blob_heap = mem_heap_create(
                                                UNIV_PAGE_SIZE);
                                }

                                data = memcpy(mem_heap_alloc(
                                                prebuilt->blob_heap, len),
                                                data, len);
                        }
                }

                if (len != UNIV_SQL_NULL) {
                        row_sel_field_store_in_mysql_format(
                                mysql_rec + templ->mysql_col_offset,
                                templ, data, len);

                        /* Cleanup */
                        if (extern_field_heap) {
                                mem_heap_free(extern_field_heap);
                                extern_field_heap = NULL;
                        }

                        if (templ->mysql_null_bit_mask) {
                                /* It is a nullable column with a non-NULL
                                value */
                                mysql_rec[templ->mysql_null_byte_offset]
                                        &= ~(byte) templ->mysql_null_bit_mask;
                        }
                } else {
                        /* MySQL assumes that the field for an SQL
                        NULL value is set to the default value. */

                        UNIV_MEM_ASSERT_RW(prebuilt->default_rec
                                           + templ->mysql_col_offset,
                                           templ->mysql_col_len);
                        mysql_rec[templ->mysql_null_byte_offset]
                                |= (byte) templ->mysql_null_bit_mask;
                        memcpy(mysql_rec + templ->mysql_col_offset,
                               (const byte*) prebuilt->default_rec
                               + templ->mysql_col_offset,
                               templ->mysql_col_len);
                }
        }

        return(TRUE);
}

/*********************************************************************//**
Builds a previous version of a clustered index record for a consistent read
@return DB_SUCCESS or error code */
static
ulint
row_sel_build_prev_vers_for_mysql(
/*==============================*/
        read_view_t*    read_view,      /*!< in: read view */
        dict_index_t*   clust_index,    /*!< in: clustered index */
        row_prebuilt_t* prebuilt,       /*!< in: prebuilt struct */
        const rec_t*    rec,            /*!< in: record in a clustered index */
        ulint**         offsets,        /*!< in/out: offsets returned by
                                        rec_get_offsets(rec, clust_index) */
        mem_heap_t**    offset_heap,    /*!< in/out: memory heap from which
                                        the offsets are allocated */
        rec_t**         old_vers,       /*!< out: old version, or NULL if the
                                        record does not exist in the view:
                                        i.e., it was freshly inserted
                                        afterwards */
        mtr_t*          mtr)            /*!< in: mtr */
{
        ulint   err;

        if (prebuilt->old_vers_heap) {
                mem_heap_empty(prebuilt->old_vers_heap);
        } else {
                prebuilt->old_vers_heap = mem_heap_create(200);
        }

        err = row_vers_build_for_consistent_read(
                rec, mtr, clust_index, offsets, read_view, offset_heap,
                prebuilt->old_vers_heap, old_vers);
        return(err);
}

/*********************************************************************//**
Retrieves the clustered index record corresponding to a record in a
non-clustered index. Does the necessary locking. Used in the MySQL
interface.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, or error code */
static
enum db_err
row_sel_get_clust_rec_for_mysql(
/*============================*/
        row_prebuilt_t* prebuilt,/*!< in: prebuilt struct in the handle */
        dict_index_t*   sec_index,/*!< in: secondary index where rec resides */
        const rec_t*    rec,    /*!< in: record in a non-clustered index; if
                                this is a locking read, then rec is not
                                allowed to be delete-marked, and that would
                                not make sense either */
        que_thr_t*      thr,    /*!< in: query thread */
        const rec_t**   out_rec,/*!< out: clustered record or an old version of
                                it, NULL if the old version did not exist
                                in the read view, i.e., it was a fresh
                                inserted version */
        ulint**         offsets,/*!< in: offsets returned by
                                rec_get_offsets(rec, sec_index);
                                out: offsets returned by
                                rec_get_offsets(out_rec, clust_index) */
        mem_heap_t**    offset_heap,/*!< in/out: memory heap from which
                                the offsets are allocated */
        mtr_t*          mtr)    /*!< in: mtr used to get access to the
                                non-clustered record; the same mtr is used to
                                access the clustered index */
{
        dict_index_t*   clust_index;
        const rec_t*    clust_rec;
        rec_t*          old_vers;
        enum db_err     err;
        trx_t*          trx;

        *out_rec = NULL;
        trx = thr_get_trx(thr);

        row_build_row_ref_in_tuple(prebuilt->clust_ref, rec,
                                   sec_index, *offsets, trx);

        clust_index = dict_table_get_first_index(sec_index->table);

        btr_pcur_open_with_no_init(clust_index, prebuilt->clust_ref,
                                   PAGE_CUR_LE, BTR_SEARCH_LEAF,
                                   prebuilt->clust_pcur, 0, mtr);

        clust_rec = btr_pcur_get_rec(prebuilt->clust_pcur);

        prebuilt->clust_pcur->trx_if_known = trx;

        /* Note: only if the search ends up on a non-infimum record is the
        low_match value the real match to the search tuple */

        if (!page_rec_is_user_rec(clust_rec)
            || btr_pcur_get_low_match(prebuilt->clust_pcur)
            < dict_index_get_n_unique(clust_index)) {

                /* In a rare case it is possible that no clust rec is found
                for a delete-marked secondary index record: if in row0umod.c
                in row_undo_mod_remove_clust_low() we have already removed
                the clust rec, while purge is still cleaning and removing
                secondary index records associated with earlier versions of
                the clustered index record. In that case we know that the
                clustered index record did not exist in the read view of
                trx. */

                if (!rec_get_deleted_flag(rec,
                                          dict_table_is_comp(sec_index->table))
                    || prebuilt->select_lock_type != LOCK_NONE) {
                        ut_print_timestamp(stderr);
                        fputs("  InnoDB: error clustered record"
                              " for sec rec not found\n"
                              "InnoDB: ", stderr);
                        dict_index_name_print(stderr, trx, sec_index);
                        fputs("\n"
                              "InnoDB: sec index record ", stderr);
                        rec_print(stderr, rec, sec_index);
                        fputs("\n"
                              "InnoDB: clust index record ", stderr);
                        rec_print(stderr, clust_rec, clust_index);
                        putc('\n', stderr);
                        trx_print(stderr, trx, 600);

                        fputs("\n"
                              "InnoDB: Submit a detailed bug report"
                              " to http://bugs.mysql.com\n", stderr);
                }

                clust_rec = NULL;

                err = DB_SUCCESS;
                goto func_exit;
        }

        *offsets = rec_get_offsets(clust_rec, clust_index, *offsets,
                                   ULINT_UNDEFINED, offset_heap);

        if (prebuilt->select_lock_type != LOCK_NONE) {
                /* Try to place a lock on the index record; we are searching
                the clust rec with a unique condition, hence
                we set a LOCK_REC_NOT_GAP type lock */

                err = lock_clust_rec_read_check_and_lock(
                        0, btr_pcur_get_block(prebuilt->clust_pcur),
                        clust_rec, clust_index, *offsets,
                        prebuilt->select_lock_type, LOCK_REC_NOT_GAP, thr);
                switch (err) {
                case DB_SUCCESS:
                case DB_SUCCESS_LOCKED_REC:
                        break;
                default:
                        goto err_exit;
                }
        } else {
                /* This is a non-locking consistent read: if necessary, fetch
                a previous version of the record */

                old_vers = NULL;

                /* If the isolation level allows reading of uncommitted data,
                then we never look for an earlier version */

                if (trx->isolation_level > TRX_ISO_READ_UNCOMMITTED
                    && !lock_clust_rec_cons_read_sees(
                            clust_rec, clust_index, *offsets,
                            trx->read_view)) {

                        /* The following call returns 'offsets' associated with
                        'old_vers' */
                        err = row_sel_build_prev_vers_for_mysql(
                                trx->read_view, clust_index, prebuilt,
                                clust_rec, offsets, offset_heap, &old_vers,
                                mtr);

                        if (err != DB_SUCCESS || old_vers == NULL) {

                                goto err_exit;
                        }

                        clust_rec = old_vers;
                }

                /* If we had to go to an earlier version of row or the
                secondary index record is delete marked, then it may be that
                the secondary index record corresponding to clust_rec
                (or old_vers) is not rec; in that case we must ignore
                such row because in our snapshot rec would not have existed.
                Remember that from rec we cannot see directly which transaction
                id corresponds to it: we have to go to the clustered index
                record. A query where we want to fetch all rows where
                the secondary index value is in some interval would return
                a wrong result if we would not drop rows which we come to
                visit through secondary index records that would not really
                exist in our snapshot. */

                if (clust_rec
                    && (old_vers
                        || trx->isolation_level <= TRX_ISO_READ_UNCOMMITTED
                        || rec_get_deleted_flag(rec, dict_table_is_comp(
                                                        sec_index->table)))
                    && !row_sel_sec_rec_is_for_clust_rec(
                            rec, sec_index, clust_rec, clust_index)) {
                        clust_rec = NULL;
#ifdef UNIV_SEARCH_DEBUG
                } else {
                        ut_a(clust_rec == NULL
                             || row_sel_sec_rec_is_for_clust_rec(
                                     rec, sec_index, clust_rec, clust_index));
#endif
                }

                err = DB_SUCCESS;
        }

func_exit:
        *out_rec = clust_rec;

        if (prebuilt->select_lock_type != LOCK_NONE) {
                /* We may use the cursor in update or in unlock_row():
                store its position */

                btr_pcur_store_position(prebuilt->clust_pcur, mtr);
        }

err_exit:
        return(err);
}

/********************************************************************//**
Restores cursor position after it has been stored. We have to take into
account that the record cursor was positioned on may have been deleted.
Then we may have to move the cursor one step up or down.
@return TRUE if we may need to process the record the cursor is now
positioned on (i.e. we should not go to the next record yet) */
static
ibool
sel_restore_position_for_mysql(
/*===========================*/
        ibool*          same_user_rec,  /*!< out: TRUE if we were able to restore
                                        the cursor on a user record with the
                                        same ordering prefix in in the
                                        B-tree index */
        ulint           latch_mode,     /*!< in: latch mode wished in
                                        restoration */
        btr_pcur_t*     pcur,           /*!< in: cursor whose position
                                        has been stored */
        ibool           moves_up,       /*!< in: TRUE if the cursor moves up
                                        in the index */
        mtr_t*          mtr)            /*!< in: mtr; CAUTION: may commit
                                        mtr temporarily! */
{
        ibool   success;
        ulint   relative_position;

        relative_position = pcur->rel_pos;

        success = btr_pcur_restore_position(latch_mode, pcur, mtr);

        *same_user_rec = success;

        if (relative_position == BTR_PCUR_ON) {
                if (success) {
                        return(FALSE);
                }

                if (moves_up) {
                        btr_pcur_move_to_next(pcur, mtr);
                }

                return(TRUE);
        }

        if (relative_position == BTR_PCUR_AFTER
            || relative_position == BTR_PCUR_AFTER_LAST_IN_TREE) {

                if (moves_up) {
                        return(TRUE);
                }

                if (btr_pcur_is_on_user_rec(pcur)) {
                        btr_pcur_move_to_prev(pcur, mtr);
                }

                return(TRUE);
        }

        ut_ad(relative_position == BTR_PCUR_BEFORE
              || relative_position == BTR_PCUR_BEFORE_FIRST_IN_TREE);

        if (moves_up && btr_pcur_is_on_user_rec(pcur)) {
                btr_pcur_move_to_next(pcur, mtr);
        }

        return(TRUE);
}

/********************************************************************//**
Copies a cached field for MySQL from the fetch cache. */
static
void
row_sel_copy_cached_field_for_mysql(
/*================================*/
        byte*                   buf,    /*!< in/out: row buffer */
        const byte*             cache,  /*!< in: cached row */
        const mysql_row_templ_t*templ)  /*!< in: column template */
{
        ulint   len;

        buf += templ->mysql_col_offset;
        cache += templ->mysql_col_offset;

        UNIV_MEM_ASSERT_W(buf, templ->mysql_col_len);

        if (templ->mysql_type == DATA_MYSQL_TRUE_VARCHAR
            && templ->type != DATA_INT) {
                /* Check for != DATA_INT to make sure we do
                not treat MySQL ENUM or SET as a true VARCHAR!
                Find the actual length of the true VARCHAR field. */
                row_mysql_read_true_varchar(
                        &len, cache, templ->mysql_length_bytes);
                len += templ->mysql_length_bytes;
                UNIV_MEM_INVALID(buf, templ->mysql_col_len);
        } else {
                len = templ->mysql_col_len;
        }

        ut_memcpy(buf, cache, len);
}

/********************************************************************//**
Pops a cached row for MySQL from the fetch cache. */
UNIV_INLINE
void
row_sel_pop_cached_row_for_mysql(
/*=============================*/
        byte*           buf,            /*!< in/out: buffer where to copy the
                                        row */
        row_prebuilt_t* prebuilt)       /*!< in: prebuilt struct */
{
        ulint                   i;
        const mysql_row_templ_t*templ;
        const byte*             cached_rec;
        ut_ad(prebuilt->n_fetch_cached > 0);
        ut_ad(prebuilt->mysql_prefix_len <= prebuilt->mysql_row_len);

        UNIV_MEM_ASSERT_W(buf, prebuilt->mysql_row_len);

        cached_rec = prebuilt->fetch_cache[prebuilt->fetch_cache_first];

        if (UNIV_UNLIKELY(prebuilt->keep_other_fields_on_keyread)) {
                /* Copy cache record field by field, don't touch fields that
                are not covered by current key */

                for (i = 0; i < prebuilt->n_template; i++) {
                        templ = prebuilt->mysql_template + i;
                        row_sel_copy_cached_field_for_mysql(
                                buf, cached_rec, templ);
                        /* Copy NULL bit of the current field from cached_rec
                        to buf */
                        if (templ->mysql_null_bit_mask) {
                                buf[templ->mysql_null_byte_offset]
                                        ^= (buf[templ->mysql_null_byte_offset]
                                            ^ cached_rec[templ->mysql_null_byte_offset])
                                        & (byte)templ->mysql_null_bit_mask;
                        }
                }
        } else if (prebuilt->mysql_prefix_len > 63) {
                /* The record is long. Copy it field by field, in case
                there are some long VARCHAR column of which only a
                small length is being used. */
                UNIV_MEM_INVALID(buf, prebuilt->mysql_prefix_len);

                /* First copy the NULL bits. */
                ut_memcpy(buf, cached_rec, prebuilt->null_bitmap_len);
                /* Then copy the requested fields. */

                for (i = 0; i < prebuilt->n_template; i++) {
                        row_sel_copy_cached_field_for_mysql(
                                buf, cached_rec, prebuilt->mysql_template + i);
                }
        } else {
                ut_memcpy(buf, cached_rec, prebuilt->mysql_prefix_len);
        }

        prebuilt->n_fetch_cached--;
        prebuilt->fetch_cache_first++;

        if (prebuilt->n_fetch_cached == 0) {
                prebuilt->fetch_cache_first = 0;
        }
}

/********************************************************************//**
Pushes a row for MySQL to the fetch cache.
@return TRUE on success, FALSE if the record contains incomplete BLOBs */
UNIV_INLINE __attribute__((warn_unused_result))
ibool
row_sel_push_cache_row_for_mysql(
/*=============================*/
        row_prebuilt_t* prebuilt,       /*!< in: prebuilt struct */
        const rec_t*    rec,            /*!< in: record to push, in the index
                                        which was described in prebuilt's
                                        template, or in the clustered index;
                                        must be protected by a page latch */
        ibool           rec_clust,      /*!< in: TRUE if rec is in the
                                        clustered index instead of
                                        prebuilt->index */
        const ulint*    offsets)        /*!< in: rec_get_offsets(rec) */
{
        byte*   buf;
        ulint   i;

        ut_ad(prebuilt->n_fetch_cached < MYSQL_FETCH_CACHE_SIZE);
        ut_ad(rec_offs_validate(rec, NULL, offsets));
        ut_ad(!rec_get_deleted_flag(rec, rec_offs_comp(offsets)));
        ut_a(!prebuilt->templ_contains_blob);

        if (prebuilt->fetch_cache[0] == NULL) {
                /* Allocate memory for the fetch cache */

                for (i = 0; i < MYSQL_FETCH_CACHE_SIZE; i++) {

                        /* A user has reported memory corruption in these
                        buffers in Linux. Put magic numbers there to help
                        to track a possible bug. */

                        buf = mem_alloc(prebuilt->mysql_row_len + 8);

                        prebuilt->fetch_cache[i] = buf + 4;

                        mach_write_to_4(buf, ROW_PREBUILT_FETCH_MAGIC_N);
                        mach_write_to_4(buf + 4 + prebuilt->mysql_row_len,
                                        ROW_PREBUILT_FETCH_MAGIC_N);
                }
        }

        ut_ad(prebuilt->fetch_cache_first == 0);
        UNIV_MEM_INVALID(prebuilt->fetch_cache[prebuilt->n_fetch_cached],
                         prebuilt->mysql_row_len);

        if (UNIV_UNLIKELY(!row_sel_store_mysql_rec(
                                  prebuilt->fetch_cache[
                                          prebuilt->n_fetch_cached],
                                  prebuilt, rec, rec_clust, offsets))) {
                return(FALSE);
        }

        prebuilt->n_fetch_cached++;
        return(TRUE);
}

/*********************************************************************//**
Tries to do a shortcut to fetch a clustered index record with a unique key,
using the hash index if possible (not always). We assume that the search
mode is PAGE_CUR_GE, it is a consistent read, there is a read view in trx,
btr search latch has been locked in S-mode.
@return SEL_FOUND, SEL_EXHAUSTED, SEL_RETRY */
static
ulint
row_sel_try_search_shortcut_for_mysql(
/*==================================*/
        const rec_t**   out_rec,/*!< out: record if found */
        row_prebuilt_t* prebuilt,/*!< in: prebuilt struct */
        ulint**         offsets,/*!< in/out: for rec_get_offsets(*out_rec) */
        mem_heap_t**    heap,   /*!< in/out: heap for rec_get_offsets() */
        mtr_t*          mtr)    /*!< in: started mtr */
{
        dict_index_t*   index           = prebuilt->index;
        const dtuple_t* search_tuple    = prebuilt->search_tuple;
        btr_pcur_t*     pcur            = prebuilt->pcur;
        trx_t*          trx             = prebuilt->trx;
        const rec_t*    rec;

        ut_ad(dict_index_is_clust(index));
        ut_ad(!prebuilt->templ_contains_blob);

#ifndef UNIV_SEARCH_DEBUG
        btr_pcur_open_with_no_init(index, search_tuple, PAGE_CUR_GE,
                                   BTR_SEARCH_LEAF, pcur,
                                   RW_S_LATCH,
                                   mtr);
#else /* UNIV_SEARCH_DEBUG */
        btr_pcur_open_with_no_init(index, search_tuple, PAGE_CUR_GE,
                                   BTR_SEARCH_LEAF, pcur,
                                   0,
                                   mtr);
#endif /* UNIV_SEARCH_DEBUG */
        rec = btr_pcur_get_rec(pcur);

        if (!page_rec_is_user_rec(rec)) {

                return(SEL_RETRY);
        }

        /* As the cursor is now placed on a user record after a search with
        the mode PAGE_CUR_GE, the up_match field in the cursor tells how many
        fields in the user record matched to the search tuple */

        if (btr_pcur_get_up_match(pcur) < dtuple_get_n_fields(search_tuple)) {

                return(SEL_EXHAUSTED);
        }

        /* This is a non-locking consistent read: if necessary, fetch
        a previous version of the record */

        *offsets = rec_get_offsets(rec, index, *offsets,
                                   ULINT_UNDEFINED, heap);

        if (!lock_clust_rec_cons_read_sees(rec, index,
                                           *offsets, trx->read_view)) {

                return(SEL_RETRY);
        }

        if (rec_get_deleted_flag(rec, dict_table_is_comp(index->table))) {

                return(SEL_EXHAUSTED);
        }

        *out_rec = rec;

        return(SEL_FOUND);
}

/********************************************************************//**
Searches for rows in the database. This is used in the interface to
MySQL. This function opens a cursor, and also implements fetch next
and fetch prev. NOTE that if we do a search with a full key value
from a unique index (ROW_SEL_EXACT), then we will not store the cursor
position and fetch next or fetch prev must not be tried to the cursor!
@return DB_SUCCESS, DB_RECORD_NOT_FOUND, DB_END_OF_INDEX, DB_DEADLOCK,
DB_LOCK_TABLE_FULL, DB_CORRUPTION, or DB_TOO_BIG_RECORD */
UNIV_INTERN
ulint
row_search_for_mysql(
/*=================*/
        byte*           buf,            /*!< in/out: buffer for the fetched
                                        row in the MySQL format */
        ulint           mode,           /*!< in: search mode PAGE_CUR_L, ... */
        row_prebuilt_t* prebuilt,       /*!< in: prebuilt struct for the
                                        table handle; this contains the info
                                        of search_tuple, index; if search
                                        tuple contains 0 fields then we
                                        position the cursor at the start or
                                        the end of the index, depending on
                                        'mode' */
        ulint           match_mode,     /*!< in: 0 or ROW_SEL_EXACT or
                                        ROW_SEL_EXACT_PREFIX */
        ulint           direction)      /*!< in: 0 or ROW_SEL_NEXT or
                                        ROW_SEL_PREV; NOTE: if this is != 0,
                                        then prebuilt must have a pcur
                                        with stored position! In opening of a
                                        cursor 'direction' should be 0. */
{
        dict_index_t*   index           = prebuilt->index;
        ibool           comp            = dict_table_is_comp(index->table);
        const dtuple_t* search_tuple    = prebuilt->search_tuple;
        btr_pcur_t*     pcur            = prebuilt->pcur;
        trx_t*          trx             = prebuilt->trx;
        dict_index_t*   clust_index;
        que_thr_t*      thr;
        const rec_t*    rec;
        const rec_t*    result_rec;
        const rec_t*    clust_rec;
        ulint           err                             = DB_SUCCESS;
        ibool           unique_search                   = FALSE;
        ibool           unique_search_from_clust_index  = FALSE;
        ibool           mtr_has_extra_clust_latch       = FALSE;
        ibool           moves_up                        = FALSE;
        ibool           set_also_gap_locks              = TRUE;
        /* if the query is a plain locking SELECT, and the isolation level
        is <= TRX_ISO_READ_COMMITTED, then this is set to FALSE */
        ibool           did_semi_consistent_read        = FALSE;
        /* if the returned record was locked and we did a semi-consistent
        read (fetch the newest committed version), then this is set to
        TRUE */
#ifdef UNIV_SEARCH_DEBUG
        ulint           cnt                             = 0;
#endif /* UNIV_SEARCH_DEBUG */
        ulint           next_offs;
        ibool           same_user_rec;
        mtr_t           mtr;
        mem_heap_t*     heap                            = NULL;
        ulint           offsets_[REC_OFFS_NORMAL_SIZE];
        ulint*          offsets                         = offsets_;
        ibool           table_lock_waited               = FALSE;

        rec_offs_init(offsets_);

        ut_ad(index && pcur && search_tuple);
        ut_ad(trx->mysql_thread_id == os_thread_get_curr_id());

        if (UNIV_UNLIKELY(prebuilt->table->ibd_file_missing)) {
                ut_print_timestamp(stderr);
                fprintf(stderr, "  InnoDB: Error:\n"
                        "InnoDB: MySQL is trying to use a table handle"
                        " but the .ibd file for\n"
                        "InnoDB: table %s does not exist.\n"
                        "InnoDB: Have you deleted the .ibd file"
                        " from the database directory under\n"
                        "InnoDB: the MySQL datadir, or have you used"
                        " DISCARD TABLESPACE?\n"
                        "InnoDB: Look from\n"
                        "InnoDB: " REFMAN "innodb-troubleshooting.html\n"
                        "InnoDB: how you can resolve the problem.\n",
                        prebuilt->table->name);

                return(DB_ERROR);
        }

        if (UNIV_UNLIKELY(!prebuilt->index_usable)) {

                return(DB_MISSING_HISTORY);
        }

        if (UNIV_UNLIKELY(prebuilt->magic_n != ROW_PREBUILT_ALLOCATED)) {
                fprintf(stderr,
                        "InnoDB: Error: trying to free a corrupt\n"
                        "InnoDB: table handle. Magic n %lu, table name ",
                        (ulong) prebuilt->magic_n);
                ut_print_name(stderr, trx, TRUE, prebuilt->table->name);
                putc('\n', stderr);

                mem_analyze_corruption(prebuilt);

                ut_error;
        }

#if 0
        /* August 19, 2005 by Heikki: temporarily disable this error
        print until the cursor lock count is done correctly.
        See bugs #12263 and #12456!*/

        if (trx->n_mysql_tables_in_use == 0
            && UNIV_UNLIKELY(prebuilt->select_lock_type == LOCK_NONE)) {
                /* Note that if MySQL uses an InnoDB temp table that it
                created inside LOCK TABLES, then n_mysql_tables_in_use can
                be zero; in that case select_lock_type is set to LOCK_X in
                ::start_stmt. */

                fputs("InnoDB: Error: MySQL is trying to perform a SELECT\n"
                      "InnoDB: but it has not locked"
                      " any tables in ::external_lock()!\n",
                      stderr);
                trx_print(stderr, trx, 600);
                fputc('\n', stderr);
        }
#endif

#if 0
        fprintf(stderr, "Match mode %lu\n search tuple ",
                (ulong) match_mode);
        dtuple_print(search_tuple);
        fprintf(stderr, "N tables locked %lu\n",
                (ulong) trx->mysql_n_tables_locked);
#endif
        /*-------------------------------------------------------------*/
        /* PHASE 0: Release a possible s-latch we are holding on the
        adaptive hash index latch if there is someone waiting behind */

        if (UNIV_UNLIKELY(rw_lock_get_writer(&btr_search_latch) != RW_LOCK_NOT_LOCKED)
            && trx->has_search_latch) {

                /* There is an x-latch request on the adaptive hash index:
                release the s-latch to reduce starvation and wait for
                BTR_SEA_TIMEOUT rounds before trying to keep it again over
                calls from MySQL */

                rw_lock_s_unlock(&btr_search_latch);
                trx->has_search_latch = FALSE;

                trx->search_latch_timeout = BTR_SEA_TIMEOUT;
        }

        /* Reset the new record lock info if srv_locks_unsafe_for_binlog
        is set or session is using a READ COMMITED isolation level. Then
        we are able to remove the record locks set here on an individual
        row. */
        prebuilt->new_rec_locks = 0;

        /*-------------------------------------------------------------*/
        /* PHASE 1: Try to pop the row from the prefetch cache */

        if (UNIV_UNLIKELY(direction == 0)) {
                trx->op_info = "starting index read";

                prebuilt->n_rows_fetched = 0;
                prebuilt->n_fetch_cached = 0;
                prebuilt->fetch_cache_first = 0;

                if (prebuilt->sel_graph == NULL) {
                        /* Build a dummy select query graph */
                        row_prebuild_sel_graph(prebuilt);
                }
        } else {
                trx->op_info = "fetching rows";

                if (prebuilt->n_rows_fetched == 0) {
                        prebuilt->fetch_direction = direction;
                }

                if (UNIV_UNLIKELY(direction != prebuilt->fetch_direction)) {
                        if (UNIV_UNLIKELY(prebuilt->n_fetch_cached > 0)) {
                                ut_error;
                                /* TODO: scrollable cursor: restore cursor to
                                the place of the latest returned row,
                                or better: prevent caching for a scroll
                                cursor! */
                        }

                        prebuilt->n_rows_fetched = 0;
                        prebuilt->n_fetch_cached = 0;
                        prebuilt->fetch_cache_first = 0;

                } else if (UNIV_LIKELY(prebuilt->n_fetch_cached > 0)) {
                        row_sel_pop_cached_row_for_mysql(buf, prebuilt);

                        prebuilt->n_rows_fetched++;

                        srv_n_rows_read++;
                        err = DB_SUCCESS;
                        goto func_exit;
                }

                if (prebuilt->fetch_cache_first > 0
                    && prebuilt->fetch_cache_first < MYSQL_FETCH_CACHE_SIZE) {

                        /* The previous returned row was popped from the fetch
                        cache, but the cache was not full at the time of the
                        popping: no more rows can exist in the result set */

                        err = DB_RECORD_NOT_FOUND;
                        goto func_exit;
                }

                prebuilt->n_rows_fetched++;

                if (prebuilt->n_rows_fetched > 1000000000) {
                        /* Prevent wrap-over */
                        prebuilt->n_rows_fetched = 500000000;
                }

                mode = pcur->search_mode;
        }

        /* In a search where at most one record in the index may match, we
        can use a LOCK_REC_NOT_GAP type record lock when locking a
        non-delete-marked matching record.

        Note that in a unique secondary index there may be different
        delete-marked versions of a record where only the primary key
        values differ: thus in a secondary index we must use next-key
        locks when locking delete-marked records. */

        if (match_mode == ROW_SEL_EXACT
            && dict_index_is_unique(index)
            && dtuple_get_n_fields(search_tuple)
            == dict_index_get_n_unique(index)
            && (dict_index_is_clust(index)
                || !dtuple_contains_null(search_tuple))) {

                /* Note above that a UNIQUE secondary index can contain many
                rows with the same key value if one of the columns is the SQL
                null. A clustered index under MySQL can never contain null
                columns because we demand that all the columns in primary key
                are non-null. */

                unique_search = TRUE;

                /* Even if the condition is unique, MySQL seems to try to
                retrieve also a second row if a primary key contains more than
                1 column. Return immediately if this is not a HANDLER
                command. */

                if (UNIV_UNLIKELY(direction != 0
                                  && !prebuilt->used_in_HANDLER)) {

                        err = DB_RECORD_NOT_FOUND;
                        goto func_exit;
                }
        }

        mtr_start(&mtr);

        /*-------------------------------------------------------------*/
        /* PHASE 2: Try fast adaptive hash index search if possible */

        /* Next test if this is the special case where we can use the fast
        adaptive hash index to try the search. Since we must release the
        search system latch when we retrieve an externally stored field, we
        cannot use the adaptive hash index in a search in the case the row
        may be long and there may be externally stored fields */

        if (UNIV_UNLIKELY(direction == 0)
            && unique_search
            && dict_index_is_clust(index)
            && !prebuilt->templ_contains_blob
            && !prebuilt->used_in_HANDLER
            && (prebuilt->mysql_row_len < UNIV_PAGE_SIZE / 8)) {

                mode = PAGE_CUR_GE;

                unique_search_from_clust_index = TRUE;

                if (trx->mysql_n_tables_locked == 0
                    && prebuilt->select_lock_type == LOCK_NONE
                    && trx->isolation_level > TRX_ISO_READ_UNCOMMITTED
                    && trx->read_view) {

                        /* This is a SELECT query done as a consistent read,
                        and the read view has already been allocated:
                        let us try a search shortcut through the hash
                        index.
                        NOTE that we must also test that
                        mysql_n_tables_locked == 0, because this might
                        also be INSERT INTO ... SELECT ... or
                        CREATE TABLE ... SELECT ... . Our algorithm is
                        NOT prepared to inserts interleaved with the SELECT,
                        and if we try that, we can deadlock on the adaptive
                        hash index semaphore! */

#ifndef UNIV_SEARCH_DEBUG
                        if (!trx->has_search_latch) {
                                rw_lock_s_lock(&btr_search_latch);
                                trx->has_search_latch = TRUE;
                        }
#endif
                        switch (row_sel_try_search_shortcut_for_mysql(
                                        &rec, prebuilt, &offsets, &heap,
                                        &mtr)) {
                        case SEL_FOUND:
#ifdef UNIV_SEARCH_DEBUG
                                ut_a(0 == cmp_dtuple_rec(search_tuple,
                                                         rec, offsets));
#endif
                                /* At this point, rec is protected by
                                a page latch that was acquired by
                                row_sel_try_search_shortcut_for_mysql().
                                The latch will not be released until
                                mtr_commit(&mtr). */
                                ut_ad(!rec_get_deleted_flag(rec, comp));

                                if (!row_sel_store_mysql_rec(buf, prebuilt,
                                                             rec, FALSE,
                                                             offsets)) {
                                        /* Only fresh inserts may contain
                                        incomplete externally stored
                                        columns. Pretend that such
                                        records do not exist. Such
                                        records may only be accessed
                                        at the READ UNCOMMITTED
                                        isolation level or when
                                        rolling back a recovered
                                        transaction. Rollback happens
                                        at a lower level, not here. */
                                        ut_a(trx->isolation_level
                                             == TRX_ISO_READ_UNCOMMITTED);

                                        /* Proceed as in case SEL_RETRY. */
                                        break;
                                }

                                mtr_commit(&mtr);

                                /* ut_print_name(stderr, index->name);
                                fputs(" shortcut\n", stderr); */

                                srv_n_rows_read++;

                                err = DB_SUCCESS;
                                goto release_search_latch_if_needed;

                        case SEL_EXHAUSTED:
                                mtr_commit(&mtr);

                                /* ut_print_name(stderr, index->name);
                                fputs(" record not found 2\n", stderr); */

                                err = DB_RECORD_NOT_FOUND;
release_search_latch_if_needed:
                                if (trx->search_latch_timeout > 0
                                    && trx->has_search_latch) {

                                        trx->search_latch_timeout--;

                                        rw_lock_s_unlock(&btr_search_latch);
                                        trx->has_search_latch = FALSE;
                                }

                                /* NOTE that we do NOT store the cursor
                                position */
                                goto func_exit;

                        case SEL_RETRY:
                                break;

                        default:
                                ut_ad(0);
                        }

                        mtr_commit(&mtr);
                        mtr_start(&mtr);
                }
        }

        /*-------------------------------------------------------------*/
        /* PHASE 3: Open or restore index cursor position */

        if (trx->has_search_latch) {
                rw_lock_s_unlock(&btr_search_latch);
                trx->has_search_latch = FALSE;
        }

        ut_ad(prebuilt->sql_stat_start || trx->conc_state == TRX_ACTIVE);
        ut_ad(trx->conc_state == TRX_NOT_STARTED
              || trx->conc_state == TRX_ACTIVE);
        ut_ad(prebuilt->sql_stat_start
              || prebuilt->select_lock_type != LOCK_NONE
              || trx->read_view);

        trx_start_if_not_started(trx);

        if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
            && prebuilt->select_lock_type != LOCK_NONE
            && trx->mysql_thd != NULL
            && thd_is_select(trx->mysql_thd)) {
                /* It is a plain locking SELECT and the isolation
                level is low: do not lock gaps */

                set_also_gap_locks = FALSE;
        }

        /* Note that if the search mode was GE or G, then the cursor
        naturally moves upward (in fetch next) in alphabetical order,
        otherwise downward */

        if (UNIV_UNLIKELY(direction == 0)) {
                if (mode == PAGE_CUR_GE || mode == PAGE_CUR_G) {
                        moves_up = TRUE;
                }
        } else if (direction == ROW_SEL_NEXT) {
                moves_up = TRUE;
        }

        thr = que_fork_get_first_thr(prebuilt->sel_graph);

        que_thr_move_to_run_state_for_mysql(thr, trx);

        clust_index = dict_table_get_first_index(index->table);

        /* Do some start-of-statement preparations */

        if (!prebuilt->sql_stat_start) {
                /* No need to set an intention lock or assign a read view */

                if (trx->read_view == NULL
                    && prebuilt->select_lock_type == LOCK_NONE) {

                        fputs("InnoDB: Error: MySQL is trying to"
                              " perform a consistent read\n"
                              "InnoDB: but the read view is not assigned!\n",
                              stderr);
                        trx_print(stderr, trx, 600);
                        fputc('\n', stderr);
                        ut_error;
                }
        } else if (prebuilt->select_lock_type == LOCK_NONE) {
                /* This is a consistent read */
                /* Assign a read view for the query */

                trx_assign_read_view(trx);
                prebuilt->sql_stat_start = FALSE;
        } else {
wait_table_again:
                err = lock_table(0, index->table,
                                 prebuilt->select_lock_type == LOCK_S
                                 ? LOCK_IS : LOCK_IX, thr);

                if (err != DB_SUCCESS) {

                        table_lock_waited = TRUE;
                        goto lock_table_wait;
                }
                prebuilt->sql_stat_start = FALSE;
        }

        /* Open or restore index cursor position */

        if (UNIV_LIKELY(direction != 0)) {
                ibool   need_to_process = sel_restore_position_for_mysql(
                        &same_user_rec, BTR_SEARCH_LEAF,
                        pcur, moves_up, &mtr);

                if (UNIV_UNLIKELY(need_to_process)) {
                        if (UNIV_UNLIKELY(prebuilt->row_read_type
                                          == ROW_READ_DID_SEMI_CONSISTENT)) {
                                /* We did a semi-consistent read,
                                but the record was removed in
                                the meantime. */
                                prebuilt->row_read_type
                                        = ROW_READ_TRY_SEMI_CONSISTENT;
                        }
                } else if (UNIV_LIKELY(prebuilt->row_read_type
                                       != ROW_READ_DID_SEMI_CONSISTENT)) {

                        /* The cursor was positioned on the record
                        that we returned previously.  If we need
                        to repeat a semi-consistent read as a
                        pessimistic locking read, the record
                        cannot be skipped. */

                        goto next_rec;
                }

        } else if (dtuple_get_n_fields(search_tuple) > 0) {

                btr_pcur_open_with_no_init(index, search_tuple, mode,
                                           BTR_SEARCH_LEAF,
                                           pcur, 0, &mtr);

                pcur->trx_if_known = trx;

                rec = btr_pcur_get_rec(pcur);

                if (!moves_up
                    && !page_rec_is_supremum(rec)
                    && set_also_gap_locks
                    && !(srv_locks_unsafe_for_binlog
                         || trx->isolation_level <= TRX_ISO_READ_COMMITTED)
                    && prebuilt->select_lock_type != LOCK_NONE) {

                        /* Try to place a gap lock on the next index record
                        to prevent phantoms in ORDER BY ... DESC queries */
                        const rec_t*    next = page_rec_get_next_const(rec);

                        offsets = rec_get_offsets(next, index, offsets,
                                                  ULINT_UNDEFINED, &heap);
                        err = sel_set_rec_lock(btr_pcur_get_block(pcur),
                                               next, index, offsets,
                                               prebuilt->select_lock_type,
                                               LOCK_GAP, thr);

                        switch (err) {
                        case DB_SUCCESS_LOCKED_REC:
                                err = DB_SUCCESS;
                        case DB_SUCCESS:
                                break;
                        default:
                                goto lock_wait_or_error;
                        }
                }
        } else {
                if (mode == PAGE_CUR_G) {
                        btr_pcur_open_at_index_side(
                                TRUE, index, BTR_SEARCH_LEAF, pcur, FALSE,
                                &mtr);
                } else if (mode == PAGE_CUR_L) {
                        btr_pcur_open_at_index_side(
                                FALSE, index, BTR_SEARCH_LEAF, pcur, FALSE,
                                &mtr);
                }
        }

rec_loop:
        DEBUG_SYNC_C("row_search_rec_loop");
        if (trx_is_interrupted(trx)) {
                btr_pcur_store_position(pcur, &mtr);
                err = DB_INTERRUPTED;
                goto normal_return;
        }

        /*-------------------------------------------------------------*/
        /* PHASE 4: Look for matching records in a loop */

        rec = btr_pcur_get_rec(pcur);
        ut_ad(!!page_rec_is_comp(rec) == comp);
#ifdef UNIV_SEARCH_DEBUG
        /*
        fputs("Using ", stderr);
        dict_index_name_print(stderr, index);
        fprintf(stderr, " cnt %lu ; Page no %lu\n", cnt,
        page_get_page_no(page_align(rec)));
        rec_print(rec);
        */
#endif /* UNIV_SEARCH_DEBUG */

        if (page_rec_is_infimum(rec)) {

                /* The infimum record on a page cannot be in the result set,
                and neither can a record lock be placed on it: we skip such
                a record. */

                goto next_rec;
        }

        if (page_rec_is_supremum(rec)) {

                if (set_also_gap_locks
                    && !(srv_locks_unsafe_for_binlog
                         || trx->isolation_level <= TRX_ISO_READ_COMMITTED)
                    && prebuilt->select_lock_type != LOCK_NONE) {

                        /* Try to place a lock on the index record */

                        /* If innodb_locks_unsafe_for_binlog option is used
                        or this session is using a READ COMMITTED isolation
                        level we do not lock gaps. Supremum record is really
                        a gap and therefore we do not set locks there. */

                        offsets = rec_get_offsets(rec, index, offsets,
                                                  ULINT_UNDEFINED, &heap);
                        err = sel_set_rec_lock(btr_pcur_get_block(pcur),
                                               rec, index, offsets,
                                               prebuilt->select_lock_type,
                                               LOCK_ORDINARY, thr);

                        switch (err) {
                        case DB_SUCCESS_LOCKED_REC:
                                err = DB_SUCCESS;
                        case DB_SUCCESS:
                                break;
                        default:
                                goto lock_wait_or_error;
                        }
                }
                /* A page supremum record cannot be in the result set: skip
                it now that we have placed a possible lock on it */

                goto next_rec;
        }

        /*-------------------------------------------------------------*/
        /* Do sanity checks in case our cursor has bumped into page
        corruption */

        if (comp) {
                next_offs = rec_get_next_offs(rec, TRUE);
                if (UNIV_UNLIKELY(next_offs < PAGE_NEW_SUPREMUM)) {

                        goto wrong_offs;
                }
        } else {
                next_offs = rec_get_next_offs(rec, FALSE);
                if (UNIV_UNLIKELY(next_offs < PAGE_OLD_SUPREMUM)) {

                        goto wrong_offs;
                }
        }

        if (UNIV_UNLIKELY(next_offs >= UNIV_PAGE_SIZE - PAGE_DIR)) {

wrong_offs:
                if (srv_force_recovery == 0 || moves_up == FALSE) {
                        ut_print_timestamp(stderr);
                        buf_page_print(page_align(rec), 0);
                        fprintf(stderr,
                                "\nInnoDB: rec address %p,"
                                " buf block fix count %lu\n",
                                (void*) rec, (ulong)
                                btr_cur_get_block(btr_pcur_get_btr_cur(pcur))
                                ->page.buf_fix_count);
                        fprintf(stderr,
                                "InnoDB: Index corruption: rec offs %lu"
                                " next offs %lu, page no %lu,\n"
                                "InnoDB: ",
                                (ulong) page_offset(rec),
                                (ulong) next_offs,
                                (ulong) page_get_page_no(page_align(rec)));
                        dict_index_name_print(stderr, trx, index);
                        fputs(". Run CHECK TABLE. You may need to\n"
                              "InnoDB: restore from a backup, or"
                              " dump + drop + reimport the table.\n",
                              stderr);

                        err = DB_CORRUPTION;

                        goto lock_wait_or_error;
                } else {
                        /* The user may be dumping a corrupt table. Jump
                        over the corruption to recover as much as possible. */

                        fprintf(stderr,
                                "InnoDB: Index corruption: rec offs %lu"
                                " next offs %lu, page no %lu,\n"
                                "InnoDB: ",
                                (ulong) page_offset(rec),
                                (ulong) next_offs,
                                (ulong) page_get_page_no(page_align(rec)));
                        dict_index_name_print(stderr, trx, index);
                        fputs(". We try to skip the rest of the page.\n",
                              stderr);

                        btr_pcur_move_to_last_on_page(pcur, &mtr);

                        goto next_rec;
                }
        }
        /*-------------------------------------------------------------*/

        /* Calculate the 'offsets' associated with 'rec' */

        offsets = rec_get_offsets(rec, index, offsets, ULINT_UNDEFINED, &heap);

        if (UNIV_UNLIKELY(srv_force_recovery > 0)) {
                if (!rec_validate(rec, offsets)
                    || !btr_index_rec_validate(rec, index, FALSE)) {
                        fprintf(stderr,
                                "InnoDB: Index corruption: rec offs %lu"
                                " next offs %lu, page no %lu,\n"
                                "InnoDB: ",
                                (ulong) page_offset(rec),
                                (ulong) next_offs,
                                (ulong) page_get_page_no(page_align(rec)));
                        dict_index_name_print(stderr, trx, index);
                        fputs(". We try to skip the record.\n",
                              stderr);

                        goto next_rec;
                }
        }

        /* Note that we cannot trust the up_match value in the cursor at this
        place because we can arrive here after moving the cursor! Thus
        we have to recompare rec and search_tuple to determine if they
        match enough. */

        if (match_mode == ROW_SEL_EXACT) {
                /* Test if the index record matches completely to search_tuple
                in prebuilt: if not, then we return with DB_RECORD_NOT_FOUND */

                /* fputs("Comparing rec and search tuple\n", stderr); */

                if (0 != cmp_dtuple_rec(search_tuple, rec, offsets)) {

                        if (set_also_gap_locks
                            && !(srv_locks_unsafe_for_binlog
                                 || trx->isolation_level
                                 <= TRX_ISO_READ_COMMITTED)
                            && prebuilt->select_lock_type != LOCK_NONE) {

                                /* Try to place a gap lock on the index
                                record only if innodb_locks_unsafe_for_binlog
                                option is not set or this session is not
                                using a READ COMMITTED isolation level. */

                                err = sel_set_rec_lock(
                                        btr_pcur_get_block(pcur),
                                        rec, index, offsets,
                                        prebuilt->select_lock_type, LOCK_GAP,
                                        thr);

                                switch (err) {
                                case DB_SUCCESS_LOCKED_REC:
                                case DB_SUCCESS:
                                        break;
                                default:
                                        goto lock_wait_or_error;
                                }
                        }

                        btr_pcur_store_position(pcur, &mtr);

                        err = DB_RECORD_NOT_FOUND;
                        /* ut_print_name(stderr, index->name);
                        fputs(" record not found 3\n", stderr); */

                        goto normal_return;
                }

        } else if (match_mode == ROW_SEL_EXACT_PREFIX) {

                if (!cmp_dtuple_is_prefix_of_rec(search_tuple, rec, offsets)) {

                        if (set_also_gap_locks
                            && !(srv_locks_unsafe_for_binlog
                                 || trx->isolation_level
                                 <= TRX_ISO_READ_COMMITTED)
                            && prebuilt->select_lock_type != LOCK_NONE) {

                                /* Try to place a gap lock on the index
                                record only if innodb_locks_unsafe_for_binlog
                                option is not set or this session is not
                                using a READ COMMITTED isolation level. */

                                err = sel_set_rec_lock(
                                        btr_pcur_get_block(pcur),
                                        rec, index, offsets,
                                        prebuilt->select_lock_type, LOCK_GAP,
                                        thr);

                                switch (err) {
                                case DB_SUCCESS_LOCKED_REC:
                                case DB_SUCCESS:
                                        break;
                                default:
                                        goto lock_wait_or_error;
                                }
                        }

                        btr_pcur_store_position(pcur, &mtr);

                        err = DB_RECORD_NOT_FOUND;
                        /* ut_print_name(stderr, index->name);
                        fputs(" record not found 4\n", stderr); */

                        goto normal_return;
                }
        }

        /* We are ready to look at a possible new index entry in the result
        set: the cursor is now placed on a user record */

        if (prebuilt->select_lock_type != LOCK_NONE) {
                /* Try to place a lock on the index record; note that delete
                marked records are a special case in a unique search. If there
                is a non-delete marked record, then it is enough to lock its
                existence with LOCK_REC_NOT_GAP. */

                /* If innodb_locks_unsafe_for_binlog option is used
                or this session is using a READ COMMITED isolation
                level we lock only the record, i.e., next-key locking is
                not used. */

                ulint   lock_type;

                if (!set_also_gap_locks
                    || srv_locks_unsafe_for_binlog
                    || trx->isolation_level <= TRX_ISO_READ_COMMITTED
                    || (unique_search
                        && !UNIV_UNLIKELY(rec_get_deleted_flag(rec, comp)))) {

                        goto no_gap_lock;
                } else {
                        lock_type = LOCK_ORDINARY;
                }

                /* If we are doing a 'greater or equal than a primary key
                value' search from a clustered index, and we find a record
                that has that exact primary key value, then there is no need
                to lock the gap before the record, because no insert in the
                gap can be in our search range. That is, no phantom row can
                appear that way.

                An example: if col1 is the primary key, the search is WHERE
                col1 >= 100, and we find a record where col1 = 100, then no
                need to lock the gap before that record. */

                if (index == clust_index
                    && mode == PAGE_CUR_GE
                    && direction == 0
                    && dtuple_get_n_fields_cmp(search_tuple)
                    == dict_index_get_n_unique(index)
                    && 0 == cmp_dtuple_rec(search_tuple, rec, offsets)) {
no_gap_lock:
                        lock_type = LOCK_REC_NOT_GAP;
                }

                err = sel_set_rec_lock(btr_pcur_get_block(pcur),
                                       rec, index, offsets,
                                       prebuilt->select_lock_type,
                                       lock_type, thr);

                switch (err) {
                        const rec_t*    old_vers;
                case DB_SUCCESS_LOCKED_REC:
                        if (srv_locks_unsafe_for_binlog
                            || trx->isolation_level
                            <= TRX_ISO_READ_COMMITTED) {
                                /* Note that a record of
                                prebuilt->index was locked. */
                                prebuilt->new_rec_locks = 1;
                        }
                        err = DB_SUCCESS;
                case DB_SUCCESS:
                        break;
                case DB_LOCK_WAIT:
                        /* Never unlock rows that were part of a conflict. */
                        prebuilt->new_rec_locks = 0;

                        if (UNIV_LIKELY(prebuilt->row_read_type
                                        != ROW_READ_TRY_SEMI_CONSISTENT)
                            || unique_search
                            || index != clust_index) {

                                goto lock_wait_or_error;
                        }

                        /* The following call returns 'offsets'
                        associated with 'old_vers' */
                        err = row_sel_build_committed_vers_for_mysql(
                                clust_index, prebuilt, rec,
                                &offsets, &heap, &old_vers, &mtr);

                        if (err != DB_SUCCESS) {

                                goto lock_wait_or_error;
                        }

                        mutex_enter(&kernel_mutex);
                        if (trx->was_chosen_as_deadlock_victim) {
                                mutex_exit(&kernel_mutex);
                                err = DB_DEADLOCK;

                                goto lock_wait_or_error;
                        }
                        if (UNIV_LIKELY(trx->wait_lock != NULL)) {
                                lock_cancel_waiting_and_release(
                                        trx->wait_lock);
                        } else {
                                mutex_exit(&kernel_mutex);

                                /* The lock was granted while we were
                                searching for the last committed version.
                                Do a normal locking read. */

                                offsets = rec_get_offsets(rec, index, offsets,
                                                          ULINT_UNDEFINED,
                                                          &heap);
                                err = DB_SUCCESS;
                                break;
                        }
                        mutex_exit(&kernel_mutex);

                        if (old_vers == NULL) {
                                /* The row was not yet committed */

                                goto next_rec;
                        }

                        did_semi_consistent_read = TRUE;
                        rec = old_vers;
                        break;
                default:

                        goto lock_wait_or_error;
                }
        } else {
                /* This is a non-locking consistent read: if necessary, fetch
                a previous version of the record */

                if (trx->isolation_level == TRX_ISO_READ_UNCOMMITTED) {

                        /* Do nothing: we let a non-locking SELECT read the
                        latest version of the record */

                } else if (index == clust_index) {

                        /* Fetch a previous version of the row if the current
                        one is not visible in the snapshot; if we have a very
                        high force recovery level set, we try to avoid crashes
                        by skipping this lookup */

                        if (UNIV_LIKELY(srv_force_recovery < 5)
                            && !lock_clust_rec_cons_read_sees(
                                    rec, index, offsets, trx->read_view)) {

                                rec_t*  old_vers;
                                /* The following call returns 'offsets'
                                associated with 'old_vers' */
                                err = row_sel_build_prev_vers_for_mysql(
                                        trx->read_view, clust_index,
                                        prebuilt, rec, &offsets, &heap,
                                        &old_vers, &mtr);

                                if (err != DB_SUCCESS) {

                                        goto lock_wait_or_error;
                                }

                                if (old_vers == NULL) {
                                        /* The row did not exist yet in
                                        the read view */

                                        goto next_rec;
                                }

                                rec = old_vers;
                        }
                } else {
                        /* We are looking into a non-clustered index,
                        and to get the right version of the record we
                        have to look also into the clustered index: this
                        is necessary, because we can only get the undo
                        information via the clustered index record. */

                        ut_ad(!dict_index_is_clust(index));

                        if (!lock_sec_rec_cons_read_sees(
                                    rec, trx->read_view)) {
                                goto requires_clust_rec;
                        }
                }
        }

        /* NOTE that at this point rec can be an old version of a clustered
        index record built for a consistent read. We cannot assume after this
        point that rec is on a buffer pool page. Functions like
        page_rec_is_comp() cannot be used! */

        if (UNIV_UNLIKELY(rec_get_deleted_flag(rec, comp))) {

                /* The record is delete-marked: we can skip it */

                if ((srv_locks_unsafe_for_binlog
                     || trx->isolation_level <= TRX_ISO_READ_COMMITTED)
                    && prebuilt->select_lock_type != LOCK_NONE
                    && !did_semi_consistent_read) {

                        /* No need to keep a lock on a delete-marked record
                        if we do not want to use next-key locking. */

                        row_unlock_for_mysql(prebuilt, TRUE);
                }

                /* This is an optimization to skip setting the next key lock
                on the record that follows this delete-marked record. This
                optimization works because of the unique search criteria
                which precludes the presence of a range lock between this
                delete marked record and the record following it.

                For now this is applicable only to clustered indexes while
                doing a unique search. There is scope for further optimization
                applicable to unique secondary indexes. Current behaviour is
                to widen the scope of a lock on an already delete marked record
                if the same record is deleted twice by the same transaction */
                if (index == clust_index && unique_search
                    && !prebuilt->used_in_HANDLER) {

                        err = DB_RECORD_NOT_FOUND;

                        goto normal_return;
                }

                goto next_rec;
        }

        /* Get the clustered index record if needed, if we did not do the
        search using the clustered index. */

        if (index != clust_index && prebuilt->need_to_access_clustered) {

requires_clust_rec:
                /* We use a 'goto' to the preceding label if a consistent
                read of a secondary index record requires us to look up old
                versions of the associated clustered index record. */

                ut_ad(rec_offs_validate(rec, index, offsets));

                /* It was a non-clustered index and we must fetch also the
                clustered index record */

                mtr_has_extra_clust_latch = TRUE;

                /* The following call returns 'offsets' associated with
                'clust_rec'. Note that 'clust_rec' can be an old version
                built for a consistent read. */

                err = row_sel_get_clust_rec_for_mysql(prebuilt, index, rec,
                                                      thr, &clust_rec,
                                                      &offsets, &heap, &mtr);
                switch (err) {
                case DB_SUCCESS:
                        if (clust_rec == NULL) {
                                /* The record did not exist in the read view */
                                ut_ad(prebuilt->select_lock_type == LOCK_NONE);

                                goto next_rec;
                        }
                        break;
                case DB_SUCCESS_LOCKED_REC:
                        ut_a(clust_rec != NULL);
                        if (srv_locks_unsafe_for_binlog
                             || trx->isolation_level
                            <= TRX_ISO_READ_COMMITTED) {
                                /* Note that the clustered index record
                                was locked. */
                                prebuilt->new_rec_locks = 2;
                        }
                        err = DB_SUCCESS;
                        break;
                default:
                        goto lock_wait_or_error;
                }

                if (UNIV_UNLIKELY(rec_get_deleted_flag(clust_rec, comp))) {

                        /* The record is delete marked: we can skip it */

                        if ((srv_locks_unsafe_for_binlog
                             || trx->isolation_level <= TRX_ISO_READ_COMMITTED)
                            && prebuilt->select_lock_type != LOCK_NONE) {

                                /* No need to keep a lock on a delete-marked
                                record if we do not want to use next-key
                                locking. */

                                row_unlock_for_mysql(prebuilt, TRUE);
                        }

                        goto next_rec;
                }

                result_rec = clust_rec;
                ut_ad(rec_offs_validate(result_rec, clust_index, offsets));
        } else {
                result_rec = rec;
        }

        /* We found a qualifying record 'result_rec'. At this point,
        'offsets' are associated with 'result_rec'. */

        ut_ad(rec_offs_validate(result_rec,
                                result_rec != rec ? clust_index : index,
                                offsets));
        ut_ad(!rec_get_deleted_flag(result_rec, comp));

        /* At this point, the clustered index record is protected
        by a page latch that was acquired when pcur was positioned.
        The latch will not be released until mtr_commit(&mtr). */

        if ((match_mode == ROW_SEL_EXACT
             || prebuilt->n_rows_fetched >= MYSQL_FETCH_CACHE_THRESHOLD)
            && prebuilt->select_lock_type == LOCK_NONE
            && !prebuilt->templ_contains_blob
            && !prebuilt->clust_index_was_generated
            && !prebuilt->used_in_HANDLER
            && prebuilt->template_type
            != ROW_MYSQL_DUMMY_TEMPLATE) {

                /* Inside an update, for example, we do not cache rows,
                since we may use the cursor position to do the actual
                update, that is why we require ...lock_type == LOCK_NONE.
                Since we keep space in prebuilt only for the BLOBs of
                a single row, we cannot cache rows in the case there
                are BLOBs in the fields to be fetched. In HANDLER we do
                not cache rows because there the cursor is a scrollable
                cursor. */

                if (!row_sel_push_cache_row_for_mysql(prebuilt, result_rec,
                                                      result_rec != rec,
                                                      offsets)) {
                        /* Only fresh inserts may contain incomplete
                        externally stored columns. Pretend that such
                        records do not exist. Such records may only be
                        accessed at the READ UNCOMMITTED isolation
                        level or when rolling back a recovered
                        transaction. Rollback happens at a lower
                        level, not here. */
                        ut_a(trx->isolation_level == TRX_ISO_READ_UNCOMMITTED);
                } else if (prebuilt->n_fetch_cached
                           == MYSQL_FETCH_CACHE_SIZE) {

                        goto got_row;
                }

                goto next_rec;
        } else {
                if (UNIV_UNLIKELY
                    (prebuilt->template_type == ROW_MYSQL_DUMMY_TEMPLATE)) {
                        /* CHECK TABLE: fetch the row */

                        if (result_rec != rec
                            && !prebuilt->need_to_access_clustered) {
                                /* We used 'offsets' for the clust
                                rec, recalculate them for 'rec' */
                                offsets = rec_get_offsets(rec, index, offsets,
                                                          ULINT_UNDEFINED,
                                                          &heap);
                                result_rec = rec;
                        }

                        memcpy(buf + 4, result_rec
                               - rec_offs_extra_size(offsets),
                               rec_offs_size(offsets));
                        mach_write_to_4(buf,
                                        rec_offs_extra_size(offsets) + 4);
                } else {
                        /* Returning a row to MySQL */

                        if (!row_sel_store_mysql_rec(buf, prebuilt, result_rec,
                                                     result_rec != rec,
                                                     offsets)) {
                                /* Only fresh inserts may contain
                                incomplete externally stored
                                columns. Pretend that such records do
                                not exist. Such records may only be
                                accessed at the READ UNCOMMITTED
                                isolation level or when rolling back a
                                recovered transaction. Rollback
                                happens at a lower level, not here. */
                                ut_a(trx->isolation_level
                                     == TRX_ISO_READ_UNCOMMITTED);
                                goto next_rec;
                        }
                }

                if (prebuilt->clust_index_was_generated) {
                        if (result_rec != rec) {
                                offsets = rec_get_offsets(
                                        rec, index, offsets, ULINT_UNDEFINED,
                                        &heap);
                        }
                        row_sel_store_row_id_to_prebuilt(prebuilt, rec,
                                                         index, offsets);
                }
        }

        /* From this point on, 'offsets' are invalid. */

got_row:
        /* We have an optimization to save CPU time: if this is a consistent
        read on a unique condition on the clustered index, then we do not
        store the pcur position, because any fetch next or prev will anyway
        return 'end of file'. Exceptions are locking reads and the MySQL
        HANDLER command where the user can move the cursor with PREV or NEXT
        even after a unique search. */

        if (!unique_search_from_clust_index
            || prebuilt->select_lock_type != LOCK_NONE
            || prebuilt->used_in_HANDLER) {

                /* Inside an update always store the cursor position */

                btr_pcur_store_position(pcur, &mtr);
        }

        err = DB_SUCCESS;

        goto normal_return;

next_rec:
        /* Reset the old and new "did semi-consistent read" flags. */
        if (UNIV_UNLIKELY(prebuilt->row_read_type
                          == ROW_READ_DID_SEMI_CONSISTENT)) {
                prebuilt->row_read_type = ROW_READ_TRY_SEMI_CONSISTENT;
        }
        did_semi_consistent_read = FALSE;
        prebuilt->new_rec_locks = 0;

        /*-------------------------------------------------------------*/
        /* PHASE 5: Move the cursor to the next index record */

        if (UNIV_UNLIKELY(mtr_has_extra_clust_latch)) {
                /* We must commit mtr if we are moving to the next
                non-clustered index record, because we could break the
                latching order if we would access a different clustered
                index page right away without releasing the previous. */

                btr_pcur_store_position(pcur, &mtr);

                mtr_commit(&mtr);
                mtr_has_extra_clust_latch = FALSE;

                mtr_start(&mtr);
                if (sel_restore_position_for_mysql(&same_user_rec,
                                                   BTR_SEARCH_LEAF,
                                                   pcur, moves_up, &mtr)) {
#ifdef UNIV_SEARCH_DEBUG
                        cnt++;
#endif /* UNIV_SEARCH_DEBUG */

                        goto rec_loop;
                }
        }

        if (moves_up) {
                if (UNIV_UNLIKELY(!btr_pcur_move_to_next(pcur, &mtr))) {
not_moved:
                        btr_pcur_store_position(pcur, &mtr);

                        if (match_mode != 0) {
                                err = DB_RECORD_NOT_FOUND;
                        } else {
                                err = DB_END_OF_INDEX;
                        }

                        goto normal_return;
                }
        } else {
                if (UNIV_UNLIKELY(!btr_pcur_move_to_prev(pcur, &mtr))) {
                        goto not_moved;
                }
        }

#ifdef UNIV_SEARCH_DEBUG
        cnt++;
#endif /* UNIV_SEARCH_DEBUG */

        goto rec_loop;

lock_wait_or_error:
        /* Reset the old and new "did semi-consistent read" flags. */
        if (UNIV_UNLIKELY(prebuilt->row_read_type
                          == ROW_READ_DID_SEMI_CONSISTENT)) {
                prebuilt->row_read_type = ROW_READ_TRY_SEMI_CONSISTENT;
        }
        did_semi_consistent_read = FALSE;

        /*-------------------------------------------------------------*/

        btr_pcur_store_position(pcur, &mtr);

lock_table_wait:
        mtr_commit(&mtr);
        mtr_has_extra_clust_latch = FALSE;

        trx->error_state = err;

        /* The following is a patch for MySQL */

        que_thr_stop_for_mysql(thr);

        thr->lock_state = QUE_THR_LOCK_ROW;

        if (row_mysql_handle_errors(&err, trx, thr, NULL)) {
                /* It was a lock wait, and it ended */

                thr->lock_state = QUE_THR_LOCK_NOLOCK;
                mtr_start(&mtr);

                /* Table lock waited, go try to obtain table lock
                again */
                if (table_lock_waited) {
                        table_lock_waited = FALSE;

                        goto wait_table_again;
                }

                sel_restore_position_for_mysql(&same_user_rec,
                                               BTR_SEARCH_LEAF, pcur,
                                               moves_up, &mtr);

                if ((srv_locks_unsafe_for_binlog
                     || trx->isolation_level <= TRX_ISO_READ_COMMITTED)
                    && !same_user_rec) {

                        /* Since we were not able to restore the cursor
                        on the same user record, we cannot use
                        row_unlock_for_mysql() to unlock any records, and
                        we must thus reset the new rec lock info. Since
                        in lock0lock.c we have blocked the inheriting of gap
                        X-locks, we actually do not have any new record locks
                        set in this case.

                        Note that if we were able to restore on the 'same'
                        user record, it is still possible that we were actually
                        waiting on a delete-marked record, and meanwhile
                        it was removed by purge and inserted again by some
                        other user. But that is no problem, because in
                        rec_loop we will again try to set a lock, and
                        new_rec_lock_info in trx will be right at the end. */

                        prebuilt->new_rec_locks = 0;
                }

                mode = pcur->search_mode;

                goto rec_loop;
        }

        thr->lock_state = QUE_THR_LOCK_NOLOCK;

#ifdef UNIV_SEARCH_DEBUG
        /*      fputs("Using ", stderr);
        dict_index_name_print(stderr, index);
        fprintf(stderr, " cnt %lu ret value %lu err\n", cnt, err); */
#endif /* UNIV_SEARCH_DEBUG */
        goto func_exit;

normal_return:
        /*-------------------------------------------------------------*/
        que_thr_stop_for_mysql_no_error(thr, trx);

        mtr_commit(&mtr);

        if (prebuilt->n_fetch_cached > 0) {
                row_sel_pop_cached_row_for_mysql(buf, prebuilt);

                err = DB_SUCCESS;
        }

#ifdef UNIV_SEARCH_DEBUG
        /*      fputs("Using ", stderr);
        dict_index_name_print(stderr, index);
        fprintf(stderr, " cnt %lu ret value %lu err\n", cnt, err); */
#endif /* UNIV_SEARCH_DEBUG */
        if (err == DB_SUCCESS) {
                srv_n_rows_read++;
        }

func_exit:
        trx->op_info = "";
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }

        /* Set or reset the "did semi-consistent read" flag on return.
        The flag did_semi_consistent_read is set if and only if
        the record being returned was fetched with a semi-consistent read. */
        ut_ad(prebuilt->row_read_type != ROW_READ_WITH_LOCKS
              || !did_semi_consistent_read);

        if (UNIV_UNLIKELY(prebuilt->row_read_type != ROW_READ_WITH_LOCKS)) {
                if (UNIV_UNLIKELY(did_semi_consistent_read)) {
                        prebuilt->row_read_type = ROW_READ_DID_SEMI_CONSISTENT;
                } else {
                        prebuilt->row_read_type = ROW_READ_TRY_SEMI_CONSISTENT;
                }
        }
        return(err);
}

/*******************************************************************//**
Checks if MySQL at the moment is allowed for this table to retrieve a
consistent read result, or store it to the query cache.
@return TRUE if storing or retrieving from the query cache is permitted */
UNIV_INTERN
ibool
row_search_check_if_query_cache_permitted(
/*======================================*/
        trx_t*          trx,            /*!< in: transaction object */
        const char*     norm_name)      /*!< in: concatenation of database name,
                                        '/' char, table name */
{
        dict_table_t*   table;
        ibool           ret     = FALSE;

        table = dict_table_get(norm_name, FALSE);

        if (table == NULL) {

                return(FALSE);
        }

        mutex_enter(&kernel_mutex);

        /* Start the transaction if it is not started yet */

        trx_start_if_not_started_low(trx);

        /* If there are locks on the table or some trx has invalidated the
        cache up to our trx id, then ret = FALSE.
        We do not check what type locks there are on the table, though only
        IX type locks actually would require ret = FALSE. */

        if (UT_LIST_GET_LEN(table->locks) == 0
            && ut_dulint_cmp(trx->id,
                             table->query_cache_inv_trx_id) >= 0) {

                ret = TRUE;

                /* If the isolation level is high, assign a read view for the
                transaction if it does not yet have one */

                if (trx->isolation_level >= TRX_ISO_REPEATABLE_READ
                    && !trx->read_view) {

                        trx->read_view = read_view_open_now(
                                trx->id, trx->global_read_view_heap);
                        trx->global_read_view = trx->read_view;
                }
        }

        mutex_exit(&kernel_mutex);

        return(ret);
}

/*******************************************************************//**
Read the AUTOINC column from the current row. If the value is less than
0 and the type is not unsigned then we reset the value to 0.
@return value read from the column */
static
ib_uint64_t
row_search_autoinc_read_column(
/*===========================*/
        dict_index_t*   index,          /*!< in: index to read from */
        const rec_t*    rec,            /*!< in: current rec */
        ulint           col_no,         /*!< in: column number */
        ulint           mtype,          /*!< in: column main type */
        ibool           unsigned_type)  /*!< in: signed or unsigned flag */
{
        ulint           len;
        const byte*     data;
        ib_uint64_t     value;
        mem_heap_t*     heap = NULL;
        ulint           offsets_[REC_OFFS_NORMAL_SIZE];
        ulint*          offsets = offsets_;

        rec_offs_init(offsets_);

        offsets = rec_get_offsets(rec, index, offsets, col_no + 1, &heap);

        if (rec_offs_nth_sql_null(offsets, col_no)) {
                /* There is no non-NULL value in the auto-increment column. */
                value = 0;
                goto func_exit;
        }

        data = rec_get_nth_field(rec, offsets, col_no, &len);

        switch (mtype) {
        case DATA_INT:
                ut_a(len <= sizeof value);
                value = mach_read_int_type(data, len, unsigned_type);
                break;

        case DATA_FLOAT:
                ut_a(len == sizeof(float));
                value = (ib_uint64_t) mach_float_read(data);
                break;

        case DATA_DOUBLE:
                ut_a(len == sizeof(double));
                value = (ib_uint64_t) mach_double_read(data);
                break;

        default:
                ut_error;
        }

        if (!unsigned_type && (ib_int64_t) value < 0) {
                value = 0;
        }

func_exit:
        if (UNIV_LIKELY_NULL(heap)) {
                mem_heap_free(heap);
        }

        return(value);
}

/*******************************************************************//**
Get the last row.
@return current rec or NULL */
static
const rec_t*
row_search_autoinc_get_rec(
/*=======================*/
        btr_pcur_t*     pcur,           /*!< in: the current cursor */
        mtr_t*          mtr)            /*!< in: mini transaction */
{
        do {
                const rec_t* rec = btr_pcur_get_rec(pcur);

                if (page_rec_is_user_rec(rec)) {
                        return(rec);
                }
        } while (btr_pcur_move_to_prev(pcur, mtr));

        return(NULL);
}

/*******************************************************************//**
Read the max AUTOINC value from an index.
@return DB_SUCCESS if all OK else error code, DB_RECORD_NOT_FOUND if
column name can't be found in index */
UNIV_INTERN
ulint
row_search_max_autoinc(
/*===================*/
        dict_index_t*   index,          /*!< in: index to search */
        const char*     col_name,       /*!< in: name of autoinc column */
        ib_uint64_t*    value)          /*!< out: AUTOINC value read */
{
        ulint           i;
        ulint           n_cols;
        dict_field_t*   dfield = NULL;
        ulint           error = DB_SUCCESS;

        n_cols = dict_index_get_n_ordering_defined_by_user(index);

        /* Search the index for the AUTOINC column name */
        for (i = 0; i < n_cols; ++i) {
                dfield = dict_index_get_nth_field(index, i);

                if (strcmp(col_name, dfield->name) == 0) {
                        break;
                }
        }

        *value = 0;

        /* Must find the AUTOINC column name */
        if (i < n_cols && dfield) {
                mtr_t           mtr;
                btr_pcur_t      pcur;

                mtr_start(&mtr);

                /* Open at the high/right end (FALSE), and INIT
                cursor (TRUE) */
                btr_pcur_open_at_index_side(
                        FALSE, index, BTR_SEARCH_LEAF, &pcur, TRUE, &mtr);

                if (page_get_n_recs(btr_pcur_get_page(&pcur)) > 0) {
                        const rec_t*    rec;

                        rec = row_search_autoinc_get_rec(&pcur, &mtr);

                        if (rec != NULL) {
                                ibool unsigned_type = (
                                        dfield->col->prtype & DATA_UNSIGNED);

                                *value = row_search_autoinc_read_column(
                                        index, rec, i,
                                        dfield->col->mtype, unsigned_type);
                        }
                }

                btr_pcur_close(&pcur);

                mtr_commit(&mtr);
        } else {
                error = DB_RECORD_NOT_FOUND;
        }

        return(error);
}