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Sourcecode: postgresql-8.4 version File versions  Download package

pg_freespacemap.c

/*-------------------------------------------------------------------------
 *
 * pg_freespacemap.c
 *      display contents of a free space map
 *
 *      $PostgreSQL: pgsql/contrib/pg_freespacemap/pg_freespacemap.c,v 1.14 2009/06/11 14:48:51 momjian Exp $
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "funcapi.h"
#include "storage/block.h"
#include "storage/freespace.h"


PG_MODULE_MAGIC;

Datum       pg_freespace(PG_FUNCTION_ARGS);

/*
 * Returns the amount of free space on a given page, according to the
 * free space map.
 */
PG_FUNCTION_INFO_V1(pg_freespace);

Datum
pg_freespace(PG_FUNCTION_ARGS)
{
      Oid               relid = PG_GETARG_OID(0);
      int64       blkno = PG_GETARG_INT64(1);
      int16       freespace;
      Relation    rel;

      rel = relation_open(relid, AccessShareLock);

      if (blkno < 0 || blkno > MaxBlockNumber)
            ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("invalid block number")));

      freespace = GetRecordedFreeSpace(rel, blkno);

      relation_close(rel, AccessShareLock);
      PG_RETURN_INT16(freespace);
}

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