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

Commitd4ffbf4

Browse files
committed
RelationTruncate() must set DELAY_CHKPT_START.
Previously, it set only DELAY_CHKPT_COMPLETE. That was important,because it meant that if the XLOG_SMGR_TRUNCATE record preceded aXLOG_CHECKPOINT_ONLINE record in the WAL, then the truncation would alsohappen on disk before the XLOG_CHECKPOINT_ONLINE record waswritten.However, it didn't guarantee that the sync request for the truncationwas processed before the XLOG_CHECKPOINT_ONLINE record was written. Bysetting DELAY_CHKPT_START, we guarantee that if an XLOG_SMGR_TRUNCATErecord is written to WAL before the redo pointer of a concurrentcheckpoint, the sync request queued by that operation must be processedby that checkpoint, rather than being left for the following one.This is a refinement of commit412ad7a. Back-patch to all supportedreleases, like that commit.Author: Robert Haas <robertmhaas@gmail.com>Reported-by: Thomas Munro <thomas.munro@gmail.com>Discussion:https://postgr.es/m/CA%2BhUKG%2B-2rjGZC2kwqr2NMLBcEBp4uf59QT1advbWYF_uc%2B0Aw%40mail.gmail.com
1 parenta963abd commitd4ffbf4

File tree

1 file changed

+20
-7
lines changed

1 file changed

+20
-7
lines changed

‎src/backend/catalog/storage.c‎

Lines changed: 20 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -337,20 +337,33 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
337337
RelationPreTruncate(rel);
338338

339339
/*
340-
*Make sure that a concurrent checkpoint can't complete while truncation
341-
*is in progress.
340+
*The code which follows can interact with concurrent checkpoints in two
341+
*separate ways.
342342
*
343-
*The truncation operation might drop buffers that the checkpoint
343+
*First, the truncation operation might drop buffers that the checkpoint
344344
* otherwise would have flushed. If it does, then it's essential that the
345345
* files actually get truncated on disk before the checkpoint record is
346346
* written. Otherwise, if reply begins from that checkpoint, the
347347
* to-be-truncated blocks might still exist on disk but have older
348348
* contents than expected, which can cause replay to fail. It's OK for the
349349
* blocks to not exist on disk at all, but not for them to have the wrong
350-
* contents.
350+
* contents. For this reason, we need to set DELAY_CHKPT_COMPLETE while
351+
* this code executes.
352+
*
353+
* Second, the call to smgrtruncate() below will in turn call
354+
* RegisterSyncRequest(). We need the sync request created by that call to
355+
* be processed before the checkpoint completes. CheckPointGuts() will
356+
* call ProcessSyncRequests(), but if we register our sync request after
357+
* that happens, then the WAL record for the truncation could end up
358+
* preceding the checkpoint record, while the actual sync doesn't happen
359+
* until the next checkpoint. To prevent that, we need to set
360+
* DELAY_CHKPT_START here. That way, if the XLOG_SMGR_TRUNCATE precedes
361+
* the redo pointer of a concurrent checkpoint, we're guaranteed that the
362+
* corresponding sync request will be processed before the checkpoint
363+
* completes.
351364
*/
352-
Assert((MyProc->delayChkptFlags&DELAY_CHKPT_COMPLETE)==0);
353-
MyProc->delayChkptFlags |=DELAY_CHKPT_COMPLETE;
365+
Assert((MyProc->delayChkptFlags&(DELAY_CHKPT_START |DELAY_CHKPT_COMPLETE))==0);
366+
MyProc->delayChkptFlags |=DELAY_CHKPT_START |DELAY_CHKPT_COMPLETE;
354367

355368
/*
356369
* We WAL-log the truncation before actually truncating, which means
@@ -398,7 +411,7 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
398411
smgrtruncate(RelationGetSmgr(rel),forks,nforks,blocks);
399412

400413
/* We've done all the critical work, so checkpoints are OK now. */
401-
MyProc->delayChkptFlags &= ~DELAY_CHKPT_COMPLETE;
414+
MyProc->delayChkptFlags &= ~(DELAY_CHKPT_START |DELAY_CHKPT_COMPLETE);
402415

403416
/*
404417
* Update upper-level FSM pages to account for the truncation. This is

0 commit comments

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