release-21.2: opt: fix missing filters after join reordering #76619
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Backport 1/2 commits from #76334.
/cc @cockroachdb/release
opt: fix missing filters after join reordering
This commit eliminates logic in the
assoc
,leftAsscom
, andrightAsscom
functions in the join order builder that aimed to preventgenerating "orphaned" predicates, where one or more referenced relations
are not in a join's input. In rare cases, this logic had the side effect
of creating invalid conflict rules for edges, which could prevent valid
predicates from being added to reordered join trees.
It is safe to remove these conditionals because they are unnecessary.
The CD-C algorithm already prevents generation of orphaned predicates by
checking that the total eligibility set (TES) is a subset of a join's
input vertices. In our implementation, this is handled by the
checkNonInnerJoin
andcheckInnerJoin
functions.Fixes #76522
Release note (bug fix): A bug has been fixed which caused the query optimizer
to omit join filters in rare cases when reordering joins, which could
result in incorrect query results. This bug was present since v20.2.
Release justification: This fixes a logical correctness bug in
the optimizer's join reordering logic.