Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit611b439

Browse files
committed
Make TransactionIdIsInProgress check transam.c's single-item XID status cache
before it goes groveling through the ProcArray. In situations where the samerecently-committed transaction ID is checked repeatedly by tqual.c, this savesa lot of shared-memory searches. And it's cheap enough that it shouldn'thurt noticeably when it doesn't help.Concept and patch by Simon, some minor tweaking and comment-cleanup by Tom.
1 parentba8a9a9 commit611b439

File tree

3 files changed

+67
-32
lines changed

3 files changed

+67
-32
lines changed

‎src/backend/access/transam/transam.c‎

Lines changed: 48 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.73 2008/01/01 19:45:48 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.74 2008/03/11 20:20:35 tgl Exp $
1212
*
1313
* NOTES
1414
* This file contains the high level access-method interface to the
@@ -25,12 +25,11 @@
2525
#include"utils/tqual.h"
2626

2727

28-
staticXidStatusTransactionLogFetch(TransactionIdtransactionId);
29-
staticvoidTransactionLogUpdate(TransactionIdtransactionId,
30-
XidStatusstatus,XLogRecPtrlsn);
31-
3228
/*
33-
* Single-item cache for results of TransactionLogFetch.
29+
* Single-item cache for results of TransactionLogFetch. It's worth having
30+
* such a cache because we frequently find ourselves repeatedly checking the
31+
* same XID, for example when scanning a table just after a bulk insert,
32+
* update, or delete.
3433
*/
3534
staticTransactionIdcachedFetchXid=InvalidTransactionId;
3635
staticXidStatuscachedFetchXidStatus;
@@ -39,9 +38,14 @@ static XLogRecPtr cachedCommitLSN;
3938
/* Handy constant for an invalid xlog recptr */
4039
staticconstXLogRecPtrInvalidXLogRecPtr= {0,0};
4140

41+
/* Local functions */
42+
staticXidStatusTransactionLogFetch(TransactionIdtransactionId);
43+
staticvoidTransactionLogUpdate(TransactionIdtransactionId,
44+
XidStatusstatus,XLogRecPtrlsn);
45+
4246

4347
/* ----------------------------------------------------------------
44-
*postgres log access method interface
48+
*Postgres log access method interface
4549
*
4650
*TransactionLogFetch
4751
*TransactionLogUpdate
@@ -82,8 +86,8 @@ TransactionLogFetch(TransactionId transactionId)
8286
xidstatus=TransactionIdGetStatus(transactionId,&xidlsn);
8387

8488
/*
85-
* DO NOT cache status for unfinished or sub-committed transactions! We
86-
* only cache status that is guaranteed not to change.
89+
*Cache it, butDO NOT cache status for unfinished or sub-committed
90+
*transactions! Weonly cache status that is guaranteed not to change.
8791
*/
8892
if (xidstatus!=TRANSACTION_STATUS_IN_PROGRESS&&
8993
xidstatus!=TRANSACTION_STATUS_SUB_COMMITTED)
@@ -96,12 +100,11 @@ TransactionLogFetch(TransactionId transactionId)
96100
returnxidstatus;
97101
}
98102

99-
/* --------------------------------
103+
/*
100104
*TransactionLogUpdate
101105
*
102106
* Store the new status of a transaction. The commit record LSN must be
103107
* passed when recording an async commit; else it should be InvalidXLogRecPtr.
104-
* --------------------------------
105108
*/
106109
staticinlinevoid
107110
TransactionLogUpdate(TransactionIdtransactionId,
@@ -131,32 +134,27 @@ TransactionLogMultiUpdate(int nxids, TransactionId *xids,
131134
TransactionIdSetStatus(xids[i],status,lsn);
132135
}
133136

137+
134138
/* ----------------------------------------------------------------
135139
*Interface functions
136140
*
137-
*TransactionId DidCommit
138-
*TransactionId DidAbort
139-
*TransactionId IsInProgress
141+
*TransactionIdDidCommit
142+
*TransactionIdDidAbort
140143
*========
141144
* these functions test the transaction status of
142145
* a specified transaction id.
143146
*
144-
*TransactionId Commit
145-
*TransactionId Abort
147+
*TransactionIdCommit
148+
*TransactionIdAbort
146149
*========
147150
* these functions set the transaction status
148151
* of the specified xid.
149152
*
153+
* See also TransactionIdIsInProgress, which once was in this module
154+
* but now lives in procarray.c.
150155
* ----------------------------------------------------------------
151156
*/
152157

153-
/* --------------------------------
154-
*TransactionId DidCommit
155-
*TransactionId DidAbort
156-
*TransactionId IsInProgress
157-
* --------------------------------
158-
*/
159-
160158
/*
161159
* TransactionIdDidCommit
162160
*True iff transaction associated with the identifier did commit.
@@ -262,11 +260,33 @@ TransactionIdDidAbort(TransactionId transactionId)
262260
return false;
263261
}
264262

265-
/* --------------------------------
266-
*TransactionId Commit
267-
*TransactionId Abort
268-
* --------------------------------
263+
/*
264+
* TransactionIdIsKnownCompleted
265+
*True iff transaction associated with the identifier is currently
266+
*known to have either committed or aborted.
267+
*
268+
* This does NOT look into pg_clog but merely probes our local cache
269+
* (and so it's not named TransactionIdDidComplete, which would be the
270+
* appropriate name for a function that worked that way). The intended
271+
* use is just to short-circuit TransactionIdIsInProgress calls when doing
272+
* repeated tqual.c checks for the same XID. If this isn't extremely fast
273+
* then it will be counterproductive.
274+
*
275+
* Note:
276+
*Assumes transaction identifier is valid.
269277
*/
278+
bool
279+
TransactionIdIsKnownCompleted(TransactionIdtransactionId)
280+
{
281+
if (TransactionIdEquals(transactionId,cachedFetchXid))
282+
{
283+
/* If it's in the cache at all, it must be completed. */
284+
return true;
285+
}
286+
287+
return false;
288+
}
289+
270290

271291
/*
272292
* TransactionIdCommit
@@ -292,7 +312,6 @@ TransactionIdAsyncCommit(TransactionId transactionId, XLogRecPtr lsn)
292312
TransactionLogUpdate(transactionId,TRANSACTION_STATUS_COMMITTED,lsn);
293313
}
294314

295-
296315
/*
297316
* TransactionIdAbort
298317
*Aborts the transaction associated with the identifier.
@@ -352,7 +371,6 @@ TransactionIdAsyncCommitTree(int nxids, TransactionId *xids, XLogRecPtr lsn)
352371
lsn);
353372
}
354373

355-
356374
/*
357375
* TransactionIdAbortTree
358376
*Marks all the given transaction ids as aborted.
@@ -368,6 +386,7 @@ TransactionIdAbortTree(int nxids, TransactionId *xids)
368386
InvalidXLogRecPtr);
369387
}
370388

389+
371390
/*
372391
* TransactionIdPrecedes --- is id1 logically < id2?
373392
*/

‎src/backend/storage/ipc/procarray.c‎

Lines changed: 17 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
*
2424
*
2525
* IDENTIFICATION
26-
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.40 2008/01/09 21:52:36 tgl Exp $
26+
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.41 2008/03/11 20:20:35 tgl Exp $
2727
*
2828
*-------------------------------------------------------------------------
2929
*/
@@ -60,6 +60,7 @@ static ProcArrayStruct *procArray;
6060

6161
/* counters for XidCache measurement */
6262
staticlongxc_by_recent_xmin=0;
63+
staticlongxc_by_known_xact=0;
6364
staticlongxc_by_my_xact=0;
6465
staticlongxc_by_latest_xid=0;
6566
staticlongxc_by_main_xid=0;
@@ -68,6 +69,7 @@ static long xc_no_overflow = 0;
6869
staticlongxc_slow_answer=0;
6970

7071
#definexc_by_recent_xmin_inc()(xc_by_recent_xmin++)
72+
#definexc_by_known_xact_inc()(xc_by_known_xact++)
7173
#definexc_by_my_xact_inc()(xc_by_my_xact++)
7274
#definexc_by_latest_xid_inc()(xc_by_latest_xid++)
7375
#definexc_by_main_xid_inc()(xc_by_main_xid++)
@@ -79,6 +81,7 @@ static void DisplayXidCache(void);
7981
#else/* !XIDCACHE_DEBUG */
8082

8183
#definexc_by_recent_xmin_inc()((void) 0)
84+
#definexc_by_known_xact_inc()((void) 0)
8285
#definexc_by_my_xact_inc()((void) 0)
8386
#definexc_by_latest_xid_inc()((void) 0)
8487
#definexc_by_main_xid_inc()((void) 0)
@@ -353,6 +356,17 @@ TransactionIdIsInProgress(TransactionId xid)
353356
return false;
354357
}
355358

359+
/*
360+
* We may have just checked the status of this transaction, so if it is
361+
* already known to be completed, we can fall out without any access to
362+
* shared memory.
363+
*/
364+
if (TransactionIdIsKnownCompleted(xid))
365+
{
366+
xc_by_known_xact_inc();
367+
return false;
368+
}
369+
356370
/*
357371
* Also, we can handle our own transaction (and subtransactions) without
358372
* any access to shared memory.
@@ -1335,8 +1349,9 @@ static void
13351349
DisplayXidCache(void)
13361350
{
13371351
fprintf(stderr,
1338-
"XidCache: xmin: %ld, myxact: %ld, latest: %ld, mainxid: %ld, childxid: %ld, nooflo: %ld, slow: %ld\n",
1352+
"XidCache: xmin: %ld,known: %ld,myxact: %ld, latest: %ld, mainxid: %ld, childxid: %ld, nooflo: %ld, slow: %ld\n",
13391353
xc_by_recent_xmin,
1354+
xc_by_known_xact,
13401355
xc_by_my_xact,
13411356
xc_by_latest_xid,
13421357
xc_by_main_xid,

‎src/include/access/transam.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/access/transam.h,v 1.64 2008/01/01 19:45:56 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/access/transam.h,v 1.65 2008/03/11 20:20:35 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -138,6 +138,7 @@ extern VariableCache ShmemVariableCache;
138138
*/
139139
externboolTransactionIdDidCommit(TransactionIdtransactionId);
140140
externboolTransactionIdDidAbort(TransactionIdtransactionId);
141+
externboolTransactionIdIsKnownCompleted(TransactionIdtransactionId);
141142
externvoidTransactionIdCommit(TransactionIdtransactionId);
142143
externvoidTransactionIdAsyncCommit(TransactionIdtransactionId,XLogRecPtrlsn);
143144
externvoidTransactionIdAbort(TransactionIdtransactionId);

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp