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release-22.2: opt: fixup CTE stats on placeholder queries #100327

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merged 1 commit into from
Apr 3, 2023

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cucaroach
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Backport 1/1 commits from #99433.

/cc @cockroachdb/release


During optbuilder phase we copy the initial expressions stats into the
fake-rel but this value can change when placeholders are assigned so add
code in AssignPlaceholders to rebuild the cte if the stats change.

Fixes: #99389
Epic: none
Release note: none

@cucaroach cucaroach requested a review from a team as a code owner March 31, 2023 17:15
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blathers-crl bot commented Mar 31, 2023

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?

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@msirek msirek left a comment

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:lgtm:

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: :shipit: complete! 1 of 0 LGTMs obtained (waiting on @yuzefovich)

During optbuilder phase we copy the initial expressions stats into the
fake-rel but this value can change when placeholders are assigned so add
code in AssignPlaceholders to rebuild the cte if the stats change.

Fixes: cockroachdb#99389
Epic: none
Release note (sql change): Prepared statements using placeholders in
recursive CTEs sometimes did not re-optimize correctly after plugging
in the parameters leading to poor plan choices, this has been fixed.
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3 participants