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47 lines
1.0 KiB
C
47 lines
1.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_freespacemap.c
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* display contents of a free space map
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*
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* contrib/pg_freespacemap/pg_freespacemap.c
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/heapam.h"
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#include "funcapi.h"
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#include "storage/block.h"
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#include "storage/freespace.h"
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PG_MODULE_MAGIC;
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Datum pg_freespace(PG_FUNCTION_ARGS);
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/*
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* Returns the amount of free space on a given page, according to the
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* free space map.
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*/
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PG_FUNCTION_INFO_V1(pg_freespace);
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Datum
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pg_freespace(PG_FUNCTION_ARGS)
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{
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Oid relid = PG_GETARG_OID(0);
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int64 blkno = PG_GETARG_INT64(1);
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int16 freespace;
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Relation rel;
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rel = relation_open(relid, AccessShareLock);
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if (blkno < 0 || blkno > MaxBlockNumber)
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("invalid block number")));
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freespace = GetRecordedFreeSpace(rel, blkno);
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relation_close(rel, AccessShareLock);
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PG_RETURN_INT16(freespace);
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}
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