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Add an EXPLAIN (BUFFERS) option to show buffer-usage statistics.

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This patch also removes buffer-usage statistics from the track_counts
output, since this (or the global server statistics) is deemed to be a better
interface to this information.

Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.
This commit is contained in:
Robert Haas
2009-12-15 04:57:48 +00:00
parent 6f1bf75d50
commit cddca5ec13
25 changed files with 274 additions and 140 deletions
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64
src/backend/storage/buffer/bufmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.252 2009/06/11 14:49:01 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.253 2009/12/15 04:57:47 rhaas Exp $
*
*-------------------------------------------------------------------------
*/
@ -34,6 +34,7 @@
#include <unistd.h>
#include "catalog/catalog.h"
#include "executor/instrument.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.h"
@ -300,22 +301,23 @@ ReadBuffer_common(SMgrRelation smgr, bool isLocalBuf, ForkNumber forkNum,
if (isLocalBuf)
{
ReadLocalBufferCount++;
bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, &found);
if (found)
LocalBufferHitCount++;
pgBufferUsage.local_blks_hit++;
else
pgBufferUsage.local_blks_read++;
}
else
{
ReadBufferCount++;
/*
* lookup the buffer. IO_IN_PROGRESS is set if the requested block is
* not currently in memory.
*/
bufHdr = BufferAlloc(smgr, forkNum, blockNum, strategy, &found);
if (found)
BufferHitCount++;
pgBufferUsage.shared_blks_hit++;
else
pgBufferUsage.shared_blks_read++;
}
/* At this point we do NOT hold any locks. */
@ -1610,54 +1612,6 @@ SyncOneBuffer(int buf_id, bool skip_recently_used)
}
/*
* Return a palloc'd string containing buffer usage statistics.
*/
char *
ShowBufferUsage(void)
{
StringInfoData str;
float hitrate;
float localhitrate;
initStringInfo(&str);
if (ReadBufferCount == 0)
hitrate = 0.0;
else
hitrate = (float) BufferHitCount *100.0 / ReadBufferCount;
if (ReadLocalBufferCount == 0)
localhitrate = 0.0;
else
localhitrate = (float) LocalBufferHitCount *100.0 / ReadLocalBufferCount;
appendStringInfo(&str,
"!\tShared blocks: %10ld read, %10ld written, buffer hit rate = %.2f%%\n",
ReadBufferCount - BufferHitCount, BufferFlushCount, hitrate);
appendStringInfo(&str,
"!\tLocal blocks: %10ld read, %10ld written, buffer hit rate = %.2f%%\n",
ReadLocalBufferCount - LocalBufferHitCount, LocalBufferFlushCount, localhitrate);
appendStringInfo(&str,
"!\tDirect blocks: %10ld read, %10ld written\n",
BufFileReadCount, BufFileWriteCount);
return str.data;
}
void
ResetBufferUsage(void)
{
BufferHitCount = 0;
ReadBufferCount = 0;
BufferFlushCount = 0;
LocalBufferHitCount = 0;
ReadLocalBufferCount = 0;
LocalBufferFlushCount = 0;
BufFileReadCount = 0;
BufFileWriteCount = 0;
}
/*
* AtEOXact_Buffers - clean up at end of transaction.
*
@ -1916,7 +1870,7 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
(char *) BufHdrGetBlock(buf),
false);
BufferFlushCount++;
pgBufferUsage.shared_blks_written++;
/*
* Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and