contrib/pageinspect/rawpage.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * rawpage.c
   4  *        Functions to extract a raw page as bytea and inspect it
   5  *
   6  * Access-method specific inspection functions are in separate files.
   7  *
   8  * Copyright (c) 2007-2008, PostgreSQL Global Development Group
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL$
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "postgres.h"
  17
  18 #include "access/heapam.h"
  19 #include "access/transam.h"
  20 #include "catalog/catalog.h"
  21 #include "catalog/namespace.h"
  22 #include "catalog/pg_type.h"
  23 #include "fmgr.h"
  24 #include "funcapi.h"
  25 #include "miscadmin.h"
  26 #include "storage/bufmgr.h"
  27 #include "utils/builtins.h"
  28
  29 PG_MODULE_MAGIC;
  30
  31 Datum           get_raw_page(PG_FUNCTION_ARGS);
  32 Datum           page_header(PG_FUNCTION_ARGS);
  33
  34 /*
  35  * get_raw_page
  36  *
  37  * Returns a copy of a page from shared buffers as a bytea
  38  */
  39 PG_FUNCTION_INFO_V1(get_raw_page);
  40
  41 Datum
  42 get_raw_page(PG_FUNCTION_ARGS)
  43 {
  44         text       *relname = PG_GETARG_TEXT_P(0);
  45         text       *forkname = PG_GETARG_TEXT_P(1);
  46         uint32          blkno = PG_GETARG_UINT32(2);
  47         ForkNumber      forknum;
  48
  49         Relation        rel;
  50         RangeVar   *relrv;
  51         bytea      *raw_page;
  52         char       *raw_page_data;
  53         Buffer          buf;
  54
  55         if (!superuser())
  56                 ereport(ERROR,
  57                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  58                                  (errmsg("must be superuser to use raw functions"))));
  59
  60         forknum = forkname_to_number(text_to_cstring(forkname));
  61
  62         relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
  63         rel = relation_openrv(relrv, AccessShareLock);
  64
  65         /* Check that this relation has storage */
  66         if (rel->rd_rel->relkind == RELKIND_VIEW)
  67                 ereport(ERROR,
  68                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
  69                                  errmsg("cannot get raw page from view \"%s\"",
  70                                                 RelationGetRelationName(rel))));
  71         if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  72                 ereport(ERROR,
  73                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
  74                                  errmsg("cannot get raw page from composite type \"%s\"",
  75                                                 RelationGetRelationName(rel))));
  76
  77         if (blkno >= RelationGetNumberOfBlocks(rel))
  78                 elog(ERROR, "block number %u is out of range for relation \"%s\"",
  79                          blkno, RelationGetRelationName(rel));
  80
  81         /* Initialize buffer to copy to */
  82         raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
  83         SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
  84         raw_page_data = VARDATA(raw_page);
  85
  86         /* Take a verbatim copy of the page */
  87
  88         buf = ReadBufferExtended(rel, forknum, blkno, RBM_NORMAL, NULL);
  89         LockBuffer(buf, BUFFER_LOCK_SHARE);
  90
  91         memcpy(raw_page_data, BufferGetPage(buf), BLCKSZ);
  92
  93         LockBuffer(buf, BUFFER_LOCK_UNLOCK);
  94         ReleaseBuffer(buf);
  95
  96         relation_close(rel, AccessShareLock);
  97
  98         PG_RETURN_BYTEA_P(raw_page);
  99 }
 100
 101 /*
 102  * page_header
 103  *
 104  * Allows inspection of page header fields of a raw page
 105  */
 106
 107 PG_FUNCTION_INFO_V1(page_header);
 108
 109 Datum
 110 page_header(PG_FUNCTION_ARGS)
 111 {
 112         bytea      *raw_page = PG_GETARG_BYTEA_P(0);
 113         int                     raw_page_size;
 114
 115         TupleDesc       tupdesc;
 116
 117         Datum           result;
 118         HeapTuple       tuple;
 119         Datum           values[9];
 120         bool            nulls[9];
 121
 122         PageHeader      page;
 123         XLogRecPtr      lsn;
 124         char            lsnchar[64];
 125
 126         if (!superuser())
 127                 ereport(ERROR,
 128                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 129                                  (errmsg("must be superuser to use raw page functions"))));
 130
 131         raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
 132
 133         /*
 134          * Check that enough data was supplied, so that we don't try to access
 135          * fields outside the supplied buffer.
 136          */
 137         if (raw_page_size < sizeof(PageHeaderData))
 138                 ereport(ERROR,
 139                                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 140                                  errmsg("input page too small (%d bytes)", raw_page_size)));
 141
 142         page = (PageHeader) VARDATA(raw_page);
 143
 144         /* Build a tuple descriptor for our result type */
 145         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 146                 elog(ERROR, "return type must be a row type");
 147
 148         /* Extract information from the page header */
 149
 150         lsn = PageGetLSN(page);
 151         snprintf(lsnchar, sizeof(lsnchar), "%X/%X", lsn.xlogid, lsn.xrecoff);
 152
 153         values[0] = CStringGetTextDatum(lsnchar);
 154         values[1] = UInt16GetDatum(PageGetTLI(page));
 155         values[2] = UInt16GetDatum(page->pd_flags);
 156         values[3] = UInt16GetDatum(page->pd_lower);
 157         values[4] = UInt16GetDatum(page->pd_upper);
 158         values[5] = UInt16GetDatum(page->pd_special);
 159         values[6] = UInt16GetDatum(PageGetPageSize(page));
 160         values[7] = UInt16GetDatum(PageGetPageLayoutVersion(page));
 161         values[8] = TransactionIdGetDatum(page->pd_prune_xid);
 162
 163         /* Build and return the tuple. */
 164
 165         memset(nulls, 0, sizeof(nulls));
 166
 167         tuple = heap_form_tuple(tupdesc, values, nulls);
 168         result = HeapTupleGetDatum(tuple);
 169
 170         PG_RETURN_DATUM(result);
 171 }