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                 : 
      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                 :  */
      21               2 : PG_FUNCTION_INFO_V1(pg_freespace);
      22                 : 
      23                 : Datum
      24              47 : pg_freespace(PG_FUNCTION_ARGS)
      25                 : {
      26              47 :     Oid         relid = PG_GETARG_OID(0);
      27              47 :     int64       blkno = PG_GETARG_INT64(1);
      28                 :     int16       freespace;
      29                 :     Relation    rel;
      30                 : 
      31              47 :     rel = relation_open(relid, AccessShareLock);
      32                 : 
      33              47 :     if (blkno < 0 || blkno > MaxBlockNumber)
      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                 : }