From f85b1a84152f7bf019fd7a2c5eede97867dcddbb Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Tue, 16 Aug 2016 08:09:15 -0400 Subject: [PATCH] Disable parallel query by default. Per discussion, set the default value of max_parallel_workers_per_gather to 0 in 9.6 only. We'll leave it enabled in master so that it gets more testing and in the hope that it can be enable by default in v10. --- doc/src/sgml/config.sgml | 2 +- src/backend/optimizer/path/costsize.c | 2 +- src/backend/utils/misc/guc.c | 2 +- src/backend/utils/misc/postgresql.conf.sample | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 02f917b375..27176aa07c 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2008,7 +2008,7 @@ include_dir 'conf.d' . Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may - be inefficient. The default value is 2. Setting this value to 0 + be inefficient. Setting this value to 0, which is the default, disables parallel query execution. diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 2a49639f12..4ad1782bbf 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -113,7 +113,7 @@ int effective_cache_size = DEFAULT_EFFECTIVE_CACHE_SIZE; Cost disable_cost = 1.0e10; -int max_parallel_workers_per_gather = 2; +int max_parallel_workers_per_gather = 0; bool enable_seqscan = true; bool enable_indexscan = true; diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 9c93df0f0a..0a58ba1fae 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2652,7 +2652,7 @@ static struct config_int ConfigureNamesInt[] = NULL }, &max_parallel_workers_per_gather, - 2, 0, 1024, + 0, 0, 1024, NULL, NULL, NULL }, diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 6d0666c44f..9644a667ff 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -163,7 +163,7 @@ #effective_io_concurrency = 1 # 1-1000; 0 disables prefetching #max_worker_processes = 8 # (change requires restart) -#max_parallel_workers_per_gather = 2 # taken from max_worker_processes +#max_parallel_workers_per_gather = 0 # taken from max_worker_processes #old_snapshot_threshold = -1 # 1min-60d; -1 disables; 0 is immediate # (change requires restart) #backend_flush_after = 0 # 0 disables, default is 0