Commit92f4786

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Additional test for each commit in sync rep path to plug minute

possibility of race condition that would effect performance only.Requested by Robert Haas. Re-arrange related comments.

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+16

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Lines changed: 16 additions & 9 deletions

Original file line number	Diff line number	Diff line change
`@@ -114,21 +114,28 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN)`
`114`	`114`	`/* Reset the latch before adding ourselves to the queue. */`
`115`	`115`	`ResetLatch(&MyProc->waitLatch);`
`116`	`116`
`117`		`-/*`
`118`		`- * Set our waitLSN so WALSender will know when to wake us, and add`
`119`		`- * ourselves to the queue.`
`120`		`- */`
`121`	`117`	`LWLockAcquire(SyncRepLock,LW_EXCLUSIVE);`
`122`	`118`	`Assert(MyProc->syncRepState==SYNC_REP_NOT_WAITING);`
`123`		`-if (!WalSndCtl->sync_standbys_defined)`
	`119`	`+`
	`120`	`+/*`
	`121`	`+ * We don't wait for sync rep if WalSndCtl->sync_standbys_defined is`
	`122`	`+ * not set. See SyncRepUpdateSyncStandbysDefined.`
	`123`	`+ *`
	`124`	`+ * Also check that the standby hasn't already replied. Unlikely`
	`125`	`+ * race condition but we'll be fetching that cache line anyway`
	`126`	`+ * so its likely to be a low cost check.`
	`127`	`+ */`
	`128`	`+if (!WalSndCtl->sync_standbys_defined\|\|`
	`129`	`+XLByteLE(XactCommitLSN,WalSndCtl->lsn))`
`124`	`130`	`{`
`125`		`-/*`
`126`		`- * We don't wait for sync rep if WalSndCtl->sync_standbys_defined is`
`127`		`- * not set. See SyncRepUpdateSyncStandbysDefined.`
`128`		`- */`
`129`	`131`	`LWLockRelease(SyncRepLock);`
`130`	`132`	`return;`
`131`	`133`	`}`
	`134`	`+`
	`135`	`+/*`
	`136`	`+ * Set our waitLSN so WALSender will know when to wake us, and add`
	`137`	`+ * ourselves to the queue.`
	`138`	`+ */`
`132`	`139`	`MyProc->waitLSN=XactCommitLSN;`
`133`	`140`	`MyProc->syncRepState=SYNC_REP_WAITING;`
`134`	`141`	`SyncRepQueueInsert();`

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