From bf08f2292ffca14fd133aa0901d1563b6ecd6894 Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Mon, 4 Apr 2016 07:18:05 +0100 Subject: [PATCH] Avoid archiving XLOG_RUNNING_XACTS on idle server If archive_timeout > 0 we should avoid logging XLOG_RUNNING_XACTS if idle. Bug 13685 reported by Laurence Rowe, investigated in detail by Michael Paquier, though this is not his proposed fix. 20151016203031.3019.72930@wrigleys.postgresql.org Simple non-invasive patch to allow later backpatch to 9.4 and 9.5 --- src/backend/postmaster/bgwriter.c | 5 ++++- src/backend/storage/ipc/standby.c | 21 +++++++++++++++++++++ 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 00f03d8acb..654e4f8bd5 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -330,8 +330,11 @@ BackgroundWriterMain(void) if (now >= timeout && last_snapshot_lsn != GetXLogInsertRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + XLogRecPtr log_standby_lsn = LogStandbySnapshot(); + last_snapshot_ts = now; + if (!XLogRecPtrIsInvalid(log_standby_lsn)) + last_snapshot_lsn = log_standby_lsn; } } diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index 6a9bf842d3..8b9b438ca9 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -902,6 +902,7 @@ LogStandbySnapshot(void) RunningTransactions running; xl_standby_lock *locks; int nlocks; + static bool last_snapshot_overflowed = false; Assert(XLogStandbyInfoActive()); @@ -932,8 +933,28 @@ LogStandbySnapshot(void) * only a shared lock. */ if (wal_level < WAL_LEVEL_LOGICAL) + { LWLockRelease(ProcArrayLock); + /* + * Don't bother to log anything if nothing is happening, if we are + * using archive_timeout > 0 and we didn't overflow snapshot last time. + * + * This ensures that we don't issue an empty WAL record, which can + * be annoying when used in conjunction with archive timeout. + */ + if (running->xcnt == 0 && + nlocks == 0 && + XLogArchiveTimeout > 0 && + !last_snapshot_overflowed) + { + LWLockRelease(XidGenLock); + return InvalidXLogRecPtr; + } + + last_snapshot_overflowed = running->subxid_overflow; + } + recptr = LogCurrentRunningXacts(running); /* Release lock if we kept it longer ... */ -- 2.40.0