db/btree/bt_overflow.c

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)bt_overflow.c       8.5 (Berkeley) 7/16/94";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/param.h>
  42
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46
  47 #include <db.h>
  48 #include "btree.h"
  49
  50 /*
  51  * Big key/data code.
  52  *
  53  * Big key and data entries are stored on linked lists of pages.  The initial
  54  * reference is byte string stored with the key or data and is the page number
  55  * and size.  The actual record is stored in a chain of pages linked by the
  56  * nextpg field of the PAGE header.
  57  *
  58  * The first page of the chain has a special property.  If the record is used
  59  * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
  60  * in the header.
  61  *
  62  * XXX
  63  * A single DBT is written to each chain, so a lot of space on the last page
  64  * is wasted.  This is a fairly major bug for some data sets.
  65  */
  66
  67 /*
  68  * __OVFL_GET -- Get an overflow key/data item.
  69  *
  70  * Parameters:
  71  *      t:      tree
  72  *      p:      pointer to { pgno_t, u_int32_t }
  73  *      buf:    storage address
  74  *      bufsz:  storage size
  75  *
  76  * Returns:
  77  *      RET_ERROR, RET_SUCCESS
  78  */
  79 int
  80 __ovfl_get(t, p, ssz, buf, bufsz)
  81         BTREE *t;
  82         void *p;
  83         size_t *ssz;
  84         void **buf;
  85         size_t *bufsz;
  86 {
  87         PAGE *h;
  88         pgno_t pg;
  89         size_t nb, plen;
  90         u_int32_t sz;
  91
  92         memmove(&pg, p, sizeof(pgno_t));
  93         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
  94         *ssz = sz;
  95
  96 #ifdef DEBUG
  97         if (pg == P_INVALID || sz == 0)
  98                 abort();
  99 #endif
 100         /* Make the buffer bigger as necessary. */
 101         if (*bufsz < sz) {
 102                 *buf = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
 103                 if (*buf == NULL)
 104                         return (RET_ERROR);
 105                 *bufsz = sz;
 106         }
 107
 108         /*
 109          * Step through the linked list of pages, copying the data on each one
 110          * into the buffer.  Never copy more than the data's length.
 111          */
 112         plen = t->bt_psize - BTDATAOFF;
 113         for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 114                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 115                         return (RET_ERROR);
 116
 117                 nb = MIN(sz, plen);
 118                 memmove(p, (char *)h + BTDATAOFF, nb);
 119                 mpool_put(t->bt_mp, h, 0);
 120
 121                 if ((sz -= nb) == 0)
 122                         break;
 123         }
 124         return (RET_SUCCESS);
 125 }
 126
 127 /*
 128  * __OVFL_PUT -- Store an overflow key/data item.
 129  *
 130  * Parameters:
 131  *      t:      tree
 132  *      data:   DBT to store
 133  *      pgno:   storage page number
 134  *
 135  * Returns:
 136  *      RET_ERROR, RET_SUCCESS
 137  */
 138 int
 139 __ovfl_put(t, dbt, pg)
 140         BTREE *t;
 141         const DBT *dbt;
 142         pgno_t *pg;
 143 {
 144         PAGE *h, *last;
 145         void *p;
 146         pgno_t npg;
 147         size_t nb, plen;
 148         u_int32_t sz;
 149
 150         /*
 151          * Allocate pages and copy the key/data record into them.  Store the
 152          * number of the first page in the chain.
 153          */
 154         plen = t->bt_psize - BTDATAOFF;
 155         for (last = NULL, p = dbt->data, sz = dbt->size;;
 156             p = (char *)p + plen, last = h) {
 157                 if ((h = __bt_new(t, &npg)) == NULL)
 158                         return (RET_ERROR);
 159
 160                 h->pgno = npg;
 161                 h->nextpg = h->prevpg = P_INVALID;
 162                 h->flags = P_OVERFLOW;
 163                 h->lower = h->upper = 0;
 164
 165                 nb = MIN(sz, plen);
 166                 memmove((char *)h + BTDATAOFF, p, nb);
 167
 168                 if (last) {
 169                         last->nextpg = h->pgno;
 170                         mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 171                 } else
 172                         *pg = h->pgno;
 173
 174                 if ((sz -= nb) == 0) {
 175                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 176                         break;
 177                 }
 178         }
 179         return (RET_SUCCESS);
 180 }
 181
 182 /*
 183  * __OVFL_DELETE -- Delete an overflow chain.
 184  *
 185  * Parameters:
 186  *      t:      tree
 187  *      p:      pointer to { pgno_t, u_int32_t }
 188  *
 189  * Returns:
 190  *      RET_ERROR, RET_SUCCESS
 191  */
 192 int
 193 __ovfl_delete(t, p)
 194         BTREE *t;
 195         void *p;
 196 {
 197         PAGE *h;
 198         pgno_t pg;
 199         size_t plen;
 200         u_int32_t sz;
 201
 202         memmove(&pg, p, sizeof(pgno_t));
 203         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
 204
 205 #ifdef DEBUG
 206         if (pg == P_INVALID || sz == 0)
 207                 abort();
 208 #endif
 209         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 210                 return (RET_ERROR);
 211
 212         /* Don't delete chains used by internal pages. */
 213         if (h->flags & P_PRESERVE) {
 214                 mpool_put(t->bt_mp, h, 0);
 215                 return (RET_SUCCESS);
 216         }
 217
 218         /* Step through the chain, calling the free routine for each page. */
 219         for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
 220                 pg = h->nextpg;
 221                 __bt_free(t, h);
 222                 if (sz <= plen)
 223                         break;
 224                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 225                         return (RET_ERROR);
 226         }
 227         return (RET_SUCCESS);
 228 }