granicus.if.org Git - postgresql/blob - 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: pgsql/contrib/pageinspect/rawpage.c,v 1.7 2008/09/30 10:52:09 heikki Exp $
  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          forknum = PG_GETARG_UINT32(1);
  45         uint32          blkno = PG_GETARG_UINT32(2);
  46
  47         Relation        rel;
  48         RangeVar   *relrv;
  49         bytea      *raw_page;
  50         char       *raw_page_data;
  51         Buffer          buf;
  52
  53         if (!superuser())
  54                 ereport(ERROR,
  55                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  56                                  (errmsg("must be superuser to use raw functions"))));
  57
  58         if (forknum > MAX_FORKNUM)
  59                 ereport(ERROR,
  60                                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  61                                  errmsg("invalid fork number")));
  62
  63         relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
  64         rel = relation_openrv(relrv, AccessShareLock);
  65
  66         /* Check that this relation has storage */
  67         if (rel->rd_rel->relkind == RELKIND_VIEW)
  68                 ereport(ERROR,
  69                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
  70                                  errmsg("cannot get raw page from view \"%s\"",
  71                                                 RelationGetRelationName(rel))));
  72         if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  73                 ereport(ERROR,
  74                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
  75                                  errmsg("cannot get raw page from composite type \"%s\"",
  76                                                 RelationGetRelationName(rel))));
  77
  78         if (blkno >= RelationGetNumberOfBlocks(rel))
  79                 elog(ERROR, "block number %u is out of range for relation \"%s\"",
  80                          blkno, RelationGetRelationName(rel));
  81
  82         /* Initialize buffer to copy to */
  83         raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
  84         SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
  85         raw_page_data = VARDATA(raw_page);
  86
  87         /* Take a verbatim copy of the page */
  88
  89         buf = ReadBufferWithFork(rel, forknum, blkno);
  90         LockBuffer(buf, BUFFER_LOCK_SHARE);
  91
  92         memcpy(raw_page_data, BufferGetPage(buf), BLCKSZ);
  93
  94         LockBuffer(buf, BUFFER_LOCK_UNLOCK);
  95         ReleaseBuffer(buf);
  96
  97         relation_close(rel, AccessShareLock);
  98
  99         PG_RETURN_BYTEA_P(raw_page);
 100 }
 101
 102 /*
 103  * page_header
 104  *
 105  * Allows inspection of page header fields of a raw page
 106  */
 107
 108 PG_FUNCTION_INFO_V1(page_header);
 109
 110 Datum
 111 page_header(PG_FUNCTION_ARGS)
 112 {
 113         bytea      *raw_page = PG_GETARG_BYTEA_P(0);
 114         int                     raw_page_size;
 115
 116         TupleDesc       tupdesc;
 117
 118         Datum           result;
 119         HeapTuple       tuple;
 120         Datum           values[9];
 121         bool            nulls[9];
 122
 123         PageHeader      page;
 124         XLogRecPtr      lsn;
 125         char            lsnchar[64];
 126
 127         if (!superuser())
 128                 ereport(ERROR,
 129                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 130                                  (errmsg("must be superuser to use raw page functions"))));
 131
 132         raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
 133
 134         /*
 135          * Check that enough data was supplied, so that we don't try to access
 136          * fields outside the supplied buffer.
 137          */
 138         if (raw_page_size < sizeof(PageHeaderData))
 139                 ereport(ERROR,
 140                                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 141                                  errmsg("input page too small (%d bytes)", raw_page_size)));
 142
 143         page = (PageHeader) VARDATA(raw_page);
 144
 145         /* Build a tuple descriptor for our result type */
 146         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 147                 elog(ERROR, "return type must be a row type");
 148
 149         /* Extract information from the page header */
 150
 151         lsn = PageGetLSN(page);
 152         snprintf(lsnchar, sizeof(lsnchar), "%X/%X", lsn.xlogid, lsn.xrecoff);
 153
 154         values[0] = CStringGetTextDatum(lsnchar);
 155         values[1] = UInt16GetDatum(PageGetTLI(page));
 156         values[2] = UInt16GetDatum(page->pd_flags);
 157         values[3] = UInt16GetDatum(page->pd_lower);
 158         values[4] = UInt16GetDatum(page->pd_upper);
 159         values[5] = UInt16GetDatum(page->pd_special);
 160         values[6] = UInt16GetDatum(PageGetPageSize(page));
 161         values[7] = UInt16GetDatum(PageGetPageLayoutVersion(page));
 162         values[8] = TransactionIdGetDatum(page->pd_prune_xid);
 163
 164         /* Build and return the tuple. */
 165
 166         memset(nulls, 0, sizeof(nulls));
 167
 168         tuple = heap_form_tuple(tupdesc, values, nulls);
 169         result = HeapTupleGetDatum(tuple);
 170
 171         PG_RETURN_DATUM(result);
 172 }