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Clarify old comment about qual_is_pushdown_safe's handling of subplans.

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This comment glossed over the difference between initplans and subplans,
but they are indeed different for our purposes here.
This commit is contained in:
Tom Lane 2017-11-28 23:32:17 -05:00
parent 3848d21673
commit 801386af62
1 changed files with 5 additions and 3 deletions
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8
src/backend/optimizer/path/allpaths.c
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@ -2840,9 +2840,11 @@ targetIsInAllPartitionLists(TargetEntry *tle, Query *query)
*
* Conditions checked here:
*
* 1. The qual must not contain any subselects (mainly because I'm not sure
* it will work correctly: sublinks will already have been transformed into
* subplans in the qual, but not in the subquery).
* 1. The qual must not contain any SubPlans (mainly because I'm not sure
* it will work correctly: SubLinks will already have been transformed into
* SubPlans in the qual, but not in the subquery). Note that SubLinks that
* transform to initplans are safe, and will be accepted here because what
* we'll see in the qual is just a Param referencing the initplan output.
*
* 2. If unsafeVolatile is set, the qual must not contain any volatile
* functions.