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Don't trust deferred-unique indexes for join removal.

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The uniqueness condition might fail to hold intra-transaction, and assuming
it does can give incorrect query results.  Per report from Marti Raudsepp,
though this is not his proposed patch.

Back-patch to 9.0, where both these features were introduced.  In the
released branches, add the new IndexOptInfo field to the end of the struct,
to try to minimize ABI breakage for third-party code that may be examining
that struct.
This commit is contained in:
Tom Lane
2011-10-23 00:43:45 -04:00
parent 8e8ac0894b
commit 18661c67e9
5 changed files with 17 additions and 4 deletions
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4
src/backend/utils/adt/selfuncs.c
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@ -4121,7 +4121,9 @@ get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo,
* commonly the same as the exposed type of the variable argument,
* but can be different in binary-compatible-type cases.
* isunique: TRUE if we were able to match the var to a unique index,
* implying its values are unique for this query.
* implying its values are unique for this query. (Caution: this
* should be trusted for statistical purposes only, since we do not
* check indimmediate.)
*
* Caller is responsible for doing ReleaseVariableStats() before exiting.
*/