opt: prevent null-rejection cycle with RightJoin #92102
Conversation
|
This change is |
There was a problem hiding this comment.
Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @DrewKimball)
-- commits line 11 at r1:
nit: CommuteRightJoin -> CommuteLeftJoin (throughout this paragraph)
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 cockroachdb#91917 Release note: None
There was a problem hiding this comment.
Reviewable status:
Previously, rytaft (Rebecca Taft) wrote…
nit: CommuteRightJoin -> CommuteLeftJoin (throughout this paragraph)
Oops, that's a good catch. CommuteRightJoin is actually right, but I need to change it below. Done.
|
TFTR! |
|
Build failed: |
|
bors r+ |
|
Build failed (retrying...): |
|
Build succeeded: |
|
Encountered an error creating backports. Some common things that can go wrong:
You might need to create your backport manually using the backport tool. error creating merge commit from d9155e1 to blathers/backport-release-22.1-92102: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict [] you may need to manually resolve merge conflicts with the backport tool. Backport to branch 22.1.x failed. See errors above. 🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is otan. |
|
Nice find! Thanks for fixing this. |
The null-rejection rules that simplify outer joins ignore RightJoin expressions because the
CommuteRightJoinrule normally converts RightJoins to LeftJoins. However, in the case whenCommuteRightJoinis disabled, we can hit a case where anIS NOT NULLfilter 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 whenCommuteRightJoinis disabled.Fixes #91917
Release note: None