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Create a third option named "partition" for constraint_exclusion, and make it

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the default.  This setting enables constraint exclusion checks only for
appendrel members (ie, inheritance children and UNION ALL arms), which are
the cases in which constraint exclusion is most likely to be useful.  Avoiding
the overhead for simple queries that are unlikely to benefit should bring
the cost down to the point where this is a reasonable default setting.
Per today's discussion.
This commit is contained in:
Tom Lane
2009-01-07 22:40:49 +00:00
parent 12dcf7bb75
commit 445ce15702
7 changed files with 92 additions and 45 deletions
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src/backend/utils/misc/postgresql.conf.sample
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@ -211,7 +211,7 @@
# - Other Planner Options -
#default_statistics_target = 100 # range 1-10000
#constraint_exclusion = off
#constraint_exclusion = partition # on, off, or partition
#cursor_tuple_fraction = 0.1 # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of explicit