From 2bef57ee8b38ee7fdbad3fb38b1f8ed31adb381b Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 15 Mar 2023 13:57:00 +1300 Subject: [PATCH] Fix fractional vacuum_cost_delay. Commit 4753ef37 changed vacuum_delay_point() to use the WaitLatch() API, to fix the problem that vacuum could keep running for a very long time after the postmaster died. Unfortunately, that broke commit caf626b2's support for fractional vacuum_cost_delay, which shipped in PostgreSQL 12. WaitLatch() works in whole milliseconds. For now, revert the change from commit 4753ef37, but add an explicit check for postmaster death. That's an extra system call on systems other than Linux and FreeBSD, but that overhead doesn't matter much considering that we willingly went to sleep and woke up again. (In later work, we might add higher resolution timeouts to the latch API so that we could do this with our standard programming pattern, but that wouldn't be back-patched.) Back-patch to 14, where commit 4753ef37 arrived. Reported-by: Melanie Plageman Discussion: https://postgr.es/m/CAAKRu_b-q0hXCBUCAATh0Z4Zi6UkiC0k2DFgoD3nC-r3SkR3tg%40mail.gmail.com --- src/backend/commands/vacuum.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 5c4bc15b44..ac69b4dc23 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -45,6 +45,7 @@ #include "postmaster/bgworker_internals.h" #include "storage/bufmgr.h" #include "storage/lmgr.h" +#include "storage/pmsignal.h" #include "storage/proc.h" #include "storage/procarray.h" #include "utils/acl.h" @@ -2171,11 +2172,18 @@ vacuum_delay_point(void) if (msec > VacuumCostDelay * 4) msec = VacuumCostDelay * 4; - (void) WaitLatch(MyLatch, - WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, - msec, - WAIT_EVENT_VACUUM_DELAY); - ResetLatch(MyLatch); + pgstat_report_wait_start(WAIT_EVENT_VACUUM_DELAY); + pg_usleep(msec * 1000); + pgstat_report_wait_end(); + + /* + * We don't want to ignore postmaster death during very long vacuums + * with vacuum_cost_delay configured. We can't use the usual + * WaitLatch() approach here because we want microsecond-based sleep + * durations above. + */ + if (IsUnderPostmaster && !PostmasterIsAlive()) + exit(1); VacuumCostBalance = 0;