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