From 5fc893760f60d57aca30163796db1abe516b3fac Mon Sep 17 00:00:00 2001 From: Kevin Grittner Date: Mon, 29 Apr 2013 13:05:26 -0500 Subject: [PATCH] Ensure ANALYZE phase is not skipped because of canceled truncate. Patch b19e4250b45e91c9cbdd18d35ea6391ab5961c8d attempted to preserve existing behavior regarding statistics generation in the case that a truncation attempt was canceled due to lock conflicts. It failed to do this accurately in two regards: (1) autovacuum had previously generated statistics if the truncate attempt failed to initially get the lock rather than having started the attempt, and (2) the VACUUM ANALYZE command had always generated statistics. Both of these changes were unintended, and are reverted by this patch. On review, there seems to be consensus that the previous failure to generate statistics when the truncate was terminated was more an unfortunate consequence of how that effort was previously terminated than a feature we want to keep; so this patch generates statistics even when an autovacuum truncation attempt terminates early. Another unintended change which is kept on the basis that it is an improvement is that when a VACUUM command is truncating, it will the new heuristic for avoiding blocking other processes, rather than keeping an AccessExclusiveLock on the table for however long the truncation takes. Per multiple reports, with some renaming per patch by Jeff Janes. Backpatch to 9.0, where problem was created. --- src/backend/commands/vacuumlazy.c | 58 ++++++++++++------------------- 1 file changed, 22 insertions(+), 36 deletions(-) diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c index d39269897a..8a1ffcf0bd 100644 --- a/src/backend/commands/vacuumlazy.c +++ b/src/backend/commands/vacuumlazy.c @@ -78,9 +78,9 @@ * that the potential for improvement was great enough to merit the cost of * supporting them. */ -#define AUTOVACUUM_TRUNCATE_LOCK_CHECK_INTERVAL 20 /* ms */ -#define AUTOVACUUM_TRUNCATE_LOCK_WAIT_INTERVAL 50 /* ms */ -#define AUTOVACUUM_TRUNCATE_LOCK_TIMEOUT 5000 /* ms */ +#define VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL 20 /* ms */ +#define VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL 50 /* ms */ +#define VACUUM_TRUNCATE_LOCK_TIMEOUT 5000 /* ms */ /* * Guesstimation of number of dead tuples per page. This is used to @@ -285,17 +285,10 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt, new_frozen_xid, new_min_multi); - /* - * Report results to the stats collector, too. An early terminated - * lazy_truncate_heap attempt suppresses the message and also cancels the - * execution of ANALYZE, if that was ordered. - */ - if (!vacrelstats->lock_waiter_detected) - pgstat_report_vacuum(RelationGetRelid(onerel), - onerel->rd_rel->relisshared, - new_rel_tuples); - else - vacstmt->options &= ~VACOPT_ANALYZE; + /* report results to the stats collector, too */ + pgstat_report_vacuum(RelationGetRelid(onerel), + onerel->rd_rel->relisshared, + new_rel_tuples); /* and log the action if appropriate */ if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0) @@ -1347,28 +1340,21 @@ lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats) */ CHECK_FOR_INTERRUPTS(); - if (++lock_retry > (AUTOVACUUM_TRUNCATE_LOCK_TIMEOUT / - AUTOVACUUM_TRUNCATE_LOCK_WAIT_INTERVAL)) + if (++lock_retry > (VACUUM_TRUNCATE_LOCK_TIMEOUT / + VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL)) { /* * We failed to establish the lock in the specified number of - * retries. This means we give up truncating. Suppress the - * ANALYZE step. Doing an ANALYZE at this point will reset the - * dead_tuple_count in the stats collector, so we will not get - * called by the autovacuum launcher again to do the truncate. + * retries. This means we give up truncating. */ vacrelstats->lock_waiter_detected = true; - ereport(LOG, - (errmsg("automatic vacuum of table \"%s.%s.%s\": " - "could not (re)acquire exclusive " - "lock for truncate scan", - get_database_name(MyDatabaseId), - get_namespace_name(RelationGetNamespace(onerel)), + ereport(elevel, + (errmsg("\"%s\": stopping truncate due to conflicting lock request", RelationGetRelationName(onerel)))); return; } - pg_usleep(AUTOVACUUM_TRUNCATE_LOCK_WAIT_INTERVAL); + pg_usleep(VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL); } /* @@ -1448,8 +1434,6 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats) { BlockNumber blkno; instr_time starttime; - instr_time currenttime; - instr_time elapsed; /* Initialize the starttime if we check for conflicting lock requests */ INSTR_TIME_SET_CURRENT(starttime); @@ -1467,24 +1451,26 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats) /* * Check if another process requests a lock on our relation. We are * holding an AccessExclusiveLock here, so they will be waiting. We - * only do this in autovacuum_truncate_lock_check millisecond - * intervals, and we only check if that interval has elapsed once - * every 32 blocks to keep the number of system calls and actual - * shared lock table lookups to a minimum. + * only do this once per VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL, and we + * only check if that interval has elapsed once every 32 blocks to + * keep the number of system calls and actual shared lock table + * lookups to a minimum. */ if ((blkno % 32) == 0) { + instr_time currenttime; + instr_time elapsed; + INSTR_TIME_SET_CURRENT(currenttime); elapsed = currenttime; INSTR_TIME_SUBTRACT(elapsed, starttime); if ((INSTR_TIME_GET_MICROSEC(elapsed) / 1000) - >= AUTOVACUUM_TRUNCATE_LOCK_CHECK_INTERVAL) + >= VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL) { if (LockHasWaitersRelation(onerel, AccessExclusiveLock)) { ereport(elevel, - (errmsg("\"%s\": suspending truncate " - "due to conflicting lock request", + (errmsg("\"%s\": suspending truncate due to conflicting lock request", RelationGetRelationName(onerel)))); vacrelstats->lock_waiter_detected = true;