From 4a78cdeb6b598940e9d9adb92deca6494628802a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 1 Aug 2007 22:45:09 +0000 Subject: Support an optional asynchronous commit mode, in which we don't flush WAL before reporting a transaction committed. Data consistency is still guaranteed (unlike setting fsync = off), but a crash may lose the effects of the last few transactions. Patch by Simon, some editorialization by Tom. --- src/backend/access/transam/xlog.c | 48 ++++++++++++++++++++++++++++++++------- 1 file changed, 40 insertions(+), 8 deletions(-) (limited to 'src/backend/access/transam/xlog.c') diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 25789ddaa68..4c7024baa38 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.275 2007/07/24 04:54:08 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.276 2007/08/01 22:45:08 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -305,6 +305,7 @@ typedef struct XLogCtlData XLogwrtResult LogwrtResult; uint32 ckptXidEpoch; /* nextXID & epoch of latest checkpoint */ TransactionId ckptXid; + XLogRecPtr asyncCommitLSN; /* LSN of newest async commit */ /* Protected by WALWriteLock: */ XLogCtlWrite Write; @@ -1643,6 +1644,22 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible, bool xlog_switch) Write->LogwrtResult = LogwrtResult; } +/* + * Record the LSN for an asynchronous transaction commit. + * (This should not be called for aborts, nor for synchronous commits.) + */ +void +XLogSetAsyncCommitLSN(XLogRecPtr asyncCommitLSN) +{ + /* use volatile pointer to prevent code rearrangement */ + volatile XLogCtlData *xlogctl = XLogCtl; + + SpinLockAcquire(&xlogctl->info_lck); + if (XLByteLT(xlogctl->asyncCommitLSN, asyncCommitLSN)) + xlogctl->asyncCommitLSN = asyncCommitLSN; + SpinLockRelease(&xlogctl->info_lck); +} + /* * Ensure that all XLOG data through the given position is flushed to disk. * @@ -1797,19 +1814,17 @@ XLogBackgroundFlush(void) /* back off to last completed page boundary */ WriteRqstPtr.xrecoff -= WriteRqstPtr.xrecoff % XLOG_BLCKSZ; -#ifdef NOT_YET /* async commit patch is still to come */ /* if we have already flushed that far, consider async commit records */ if (XLByteLE(WriteRqstPtr, LogwrtResult.Flush)) { /* use volatile pointer to prevent code rearrangement */ volatile XLogCtlData *xlogctl = XLogCtl; - SpinLockAcquire(&xlogctl->async_commit_lck); + SpinLockAcquire(&xlogctl->info_lck); WriteRqstPtr = xlogctl->asyncCommitLSN; - SpinLockRelease(&xlogctl->async_commit_lck); + SpinLockRelease(&xlogctl->info_lck); flexible = false; /* ensure it all gets written */ } -#endif /* Done if already known flushed */ if (XLByteLE(WriteRqstPtr, LogwrtResult.Flush)) @@ -1841,6 +1856,23 @@ XLogBackgroundFlush(void) END_CRIT_SECTION(); } +/* + * Flush any previous asynchronously-committed transactions' commit records. + */ +void +XLogAsyncCommitFlush(void) +{ + XLogRecPtr WriteRqstPtr; + /* use volatile pointer to prevent code rearrangement */ + volatile XLogCtlData *xlogctl = XLogCtl; + + SpinLockAcquire(&xlogctl->info_lck); + WriteRqstPtr = xlogctl->asyncCommitLSN; + SpinLockRelease(&xlogctl->info_lck); + + XLogFlush(WriteRqstPtr); +} + /* * Test whether XLOG data has been flushed up to (at least) the given position. * @@ -5466,7 +5498,7 @@ ShutdownXLOG(int code, Datum arg) (errmsg("database system is shut down"))); } -/* +/* * Log start of a checkpoint. */ static void @@ -5481,7 +5513,7 @@ LogCheckpointStart(int flags) (flags & CHECKPOINT_CAUSE_TIME) ? " time" : ""); } -/* +/* * Log end of a checkpoint. */ static void @@ -5523,7 +5555,7 @@ LogCheckpointEnd(void) * flags is a bitwise OR of the following: * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown. * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP, - * ignoring checkpoint_completion_target parameter. + * ignoring checkpoint_completion_target parameter. * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured * since the last one (implied by CHECKPOINT_IS_SHUTDOWN). * -- cgit v1.2.3