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/*
* $Header: /cvsroot/pgsql/contrib/pgstattuple/pgstattuple.c,v 1.6 2002/05/20 23:51:40 tgl Exp $
*
* Copyright (c) 2001 Tatsuo Ishii
*
* Permission to use, copy, modify, and distribute this software and
* its documentation for any purpose, without fee, and without a
* written agreement is hereby granted, provided that the above
* copyright notice and this paragraph and the following two
* paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
* IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
* SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
#include "postgres.h"
#include "fmgr.h"
#include "access/heapam.h"
#include "access/transam.h"
#include "catalog/namespace.h"
#include "utils/builtins.h"
PG_FUNCTION_INFO_V1(pgstattuple);
extern Datum pgstattuple(PG_FUNCTION_ARGS);
/* ----------
* pgstattuple:
* returns the percentage of dead tuples
*
* C FUNCTION definition
* pgstattuple(NAME) returns FLOAT8
* ----------
*/
Datum
pgstattuple(PG_FUNCTION_ARGS)
{
text *relname = PG_GETARG_TEXT_P(0);
RangeVar *relrv;
Relation rel;
HeapScanDesc scan;
HeapTuple tuple;
BlockNumber nblocks;
BlockNumber block = 0; /* next block to count free space in */
BlockNumber tupblock;
Buffer buffer;
double table_len;
uint64 tuple_len = 0;
uint64 dead_tuple_len = 0;
uint64 tuple_count = 0;
uint64 dead_tuple_count = 0;
double tuple_percent;
double dead_tuple_percent;
uint64 free_space = 0; /* free/reusable space in bytes */
double free_percent; /* free/reusable space in % */
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname,
"pgstattuple"));
rel = heap_openrv(relrv, AccessShareLock);
nblocks = RelationGetNumberOfBlocks(rel);
scan = heap_beginscan(rel, SnapshotAny, 0, NULL);
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
if (HeapTupleSatisfiesNow(tuple->t_data))
{
tuple_len += tuple->t_len;
tuple_count++;
}
else
{
dead_tuple_len += tuple->t_len;
dead_tuple_count++;
}
/*
* To avoid physically reading the table twice, try to do the
* free-space scan in parallel with the heap scan. However,
* heap_getnext may find no tuples on a given page, so we cannot
* simply examine the pages returned by the heap scan.
*/
tupblock = BlockIdGetBlockNumber(&tuple->t_self.ip_blkid);
while (block <= tupblock)
{
buffer = ReadBuffer(rel, block);
free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
ReleaseBuffer(buffer);
block++;
}
}
heap_endscan(scan);
while (block < nblocks)
{
buffer = ReadBuffer(rel, block);
free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
ReleaseBuffer(buffer);
block++;
}
heap_close(rel, AccessShareLock);
table_len = (double) nblocks *BLCKSZ;
if (nblocks == 0)
{
tuple_percent = 0.0;
dead_tuple_percent = 0.0;
free_percent = 0.0;
}
else
{
tuple_percent = (double) tuple_len *100.0 / table_len;
dead_tuple_percent = (double) dead_tuple_len *100.0 / table_len;
free_percent = (double) free_space *100.0 / table_len;
}
elog(DEBUG3, "physical length: %.2fMB live tuples: %.0f (%.2fMB, %.2f%%) dead tuples: %.0f (%.2fMB, %.2f%%) free/reusable space: %.2fMB (%.2f%%) overhead: %.2f%%",
table_len / (1024 * 1024), /* physical length in MB */
(double) tuple_count, /* number of live tuples */
(double) tuple_len / (1024 * 1024), /* live tuples in MB */
tuple_percent, /* live tuples in % */
(double) dead_tuple_count, /* number of dead tuples */
(double) dead_tuple_len / (1024 * 1024), /* dead tuples in MB */
dead_tuple_percent, /* dead tuples in % */
(double) free_space / (1024 * 1024), /* free/available space in
* MB */
free_percent, /* free/available space in % */
/* overhead in % */
(nblocks == 0) ? 0.0 : 100.0
- tuple_percent
- dead_tuple_percent
- free_percent);
PG_RETURN_FLOAT8(dead_tuple_percent);
}
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