1 /*-------------------------------------------------------------------------
4 * display contents of a free space map
6 * $PostgreSQL: pgsql/contrib/pg_freespacemap/pg_freespacemap.c,v 1.14 2009/06/11 14:48:51 momjian Exp $
7 *-------------------------------------------------------------------------
11 #include "access/heapam.h"
13 #include "storage/block.h"
14 #include "storage/freespace.h"
19 Datum pg_freespace(PG_FUNCTION_ARGS);
22 * Returns the amount of free space on a given page, according to the
25 PG_FUNCTION_INFO_V1(pg_freespace);
28 pg_freespace(PG_FUNCTION_ARGS)
30 Oid relid = PG_GETARG_OID(0);
31 int64 blkno = PG_GETARG_INT64(1);
35 rel = relation_open(relid, AccessShareLock);
37 if (blkno < 0 || blkno > MaxBlockNumber)
39 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
40 errmsg("invalid block number")));
42 freespace = GetRecordedFreeSpace(rel, blkno);
44 relation_close(rel, AccessShareLock);
45 PG_RETURN_INT16(freespace);