Age Owner TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pg_freespacemap.c
4 : * display contents of a free space map
5 : *
6 : * contrib/pg_freespacemap/pg_freespacemap.c
7 : *-------------------------------------------------------------------------
8 : */
9 : #include "postgres.h"
10 :
11 : #include "access/relation.h"
12 : #include "funcapi.h"
13 : #include "storage/freespace.h"
14 :
6158 tgl 15 CBC 1 : PG_MODULE_MAGIC;
16 :
17 : /*
18 : * Returns the amount of free space on a given page, according to the
19 : * free space map.
20 : */
5304 heikki.linnakangas 21 2 : PG_FUNCTION_INFO_V1(pg_freespace);
22 :
23 : Datum
24 47 : pg_freespace(PG_FUNCTION_ARGS)
25 : {
5050 bruce 26 47 : Oid relid = PG_GETARG_OID(0);
27 47 : int64 blkno = PG_GETARG_INT64(1);
28 : int16 freespace;
29 : Relation rel;
30 :
5304 heikki.linnakangas 31 47 : rel = relation_open(relid, AccessShareLock);
32 :
5302 33 47 : if (blkno < 0 || blkno > MaxBlockNumber)
5304 34 2 : ereport(ERROR,
35 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
36 : errmsg("invalid block number")));
37 :
38 45 : freespace = GetRecordedFreeSpace(rel, blkno);
39 :
40 45 : relation_close(rel, AccessShareLock);
41 45 : PG_RETURN_INT16(freespace);
42 : }
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