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Disable parallel query by default.

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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.
This commit is contained in:
Robert Haas 2016-08-16 08:09:15 -04:00
parent b5bce6c1ec
commit f85b1a8415
4 changed files with 4 additions and 4 deletions
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2
doc/src/sgml/config.sgml
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@ -2008,7 +2008,7 @@ include_dir 'conf.d'
<xref linkend="guc-max-worker-processes">. 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.
</para>

2
src/backend/optimizer/path/costsize.c
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@ -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;

2
src/backend/utils/misc/guc.c
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@ -2652,7 +2652,7 @@ static struct config_int ConfigureNamesInt[] =
NULL
},
&max_parallel_workers_per_gather,
2, 0, 1024,
0, 0, 1024,
NULL, NULL, NULL
},

2
src/backend/utils/misc/postgresql.conf.sample
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@ -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