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release-22.2: opt: prevent null-rejection cycle with RightJoin #92661

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merged 1 commit into from
Nov 29, 2022
Merged

release-22.2: opt: prevent null-rejection cycle with RightJoin #92661

merged 1 commit into from
Nov 29, 2022

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@blathers-crl blathers-crl bot commented Nov 29, 2022 •
edited by DrewKimball
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Backport 1/1 commits from #92102 on behalf of @DrewKimball.

/cc @cockroachdb/release

The null-rejection rules that simplify outer joins ignore RightJoin expressions because the CommuteRightJoin rule normally converts RightJoins to LeftJoins. However, in the case when CommuteRightJoin is disabled, we can hit a case where an IS NOT NULL filter gets pushed down but then gets pulled back up by decorrelation rules when it can't simplify the RightJoin, causing a cycle. This patch fixes the problem by preventing RightJoins from requesting null-rejection when CommuteRightJoin is disabled.

Fixes #91917

Release note: None

Release justification: testing-only change

@DrewKimball
opt: prevent null-rejection cycle with RightJoin
b8fef9c 
The null-rejection rules that simplify outer joins ignore RightJoin
expressions because the `CommuteRightJoin` rule normally converts
RightJoins to LeftJoins. However, in the case when `CommuteRightJoin`
is disabled, we can hit a case where an `IS NOT NULL` filter gets
pushed down but then gets pulled back up by decorrelation rules when
it can't simplify the RightJoin, causing a cycle. This patch fixes
the problem by preventing RightJoins from requesting null-rejection
when `CommuteRightJoin` is disabled.

Fixes #91917

Release note: None
@blathers-crl blathers-crl bot requested a review from a team as a code owner November 29, 2022 11:49
@blathers-crl blathers-crl bot force-pushed the blathers/backport-release-22.2-92102 branch from 3616f73 to b8fef9c Compare November 29, 2022 11:49
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blathers-crl bot commented Nov 29, 2022 •
edited by DrewKimball
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Thanks for opening a backport.

Please check the backport criteria before merging:

  • Patches should only be created for serious issues or test-only changes.
  • Patches should not break backwards-compatibility.
  • Patches should change as little code as possible.
  • Patches should not change on-disk formats or node communication protocols.
  • Patches should not add new functionality.
  • Patches must not add, edit, or otherwise modify cluster versions; or add version gates.
If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.
  • There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
  • The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
  • New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
  • The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

  • What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
  • Will this work in a cluster of mixed patch versions? Did we test that?
  • If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

@blathers-crl blathers-crl bot requested review from DrewKimball and rytaft November 29, 2022 11:49
@blathers-crl blathers-crl bot added blathers-backport This is a backport that Blathers created automatically. O-robot Originated from a bot. labels Nov 29, 2022
mgartner
mgartner approved these changes Nov 29, 2022
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LGTM

@DrewKimball
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TFTR!

@DrewKimball DrewKimball merged commit 90f8016 into release-22.2 Nov 29, 2022
@DrewKimball DrewKimball deleted the blathers/backport-release-22.2-92102 branch November 29, 2022 21:12
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@mgartner mgartner mgartner approved these changes

@DrewKimball DrewKimball Awaiting requested review from DrewKimball

@rytaft rytaft Awaiting requested review from rytaft

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