opt: fix error caused by recursive CTE with zero rows on left side#49961
Merged
craig[bot] merged 1 commit intocockroachdb:masterfrom Jun 8, 2020
Merged
opt: fix error caused by recursive CTE with zero rows on left side#49961craig[bot] merged 1 commit intocockroachdb:masterfrom
craig[bot] merged 1 commit intocockroachdb:masterfrom
Conversation
Prior to this commit, a recursive CTE in which the cardinality of the left side of the UNION ALL expression was zero would cause an error in the statistics code, "estimated row count must be non-zero". This was happening because the cardinality of the recursive CTE binding props was set to be non-zero, but the row count, which came from the left side expression, was not updated accordingly. The stats code only allows the row count to be zero if the cardinality is also zero. This commit fixes the problem by setting the row count of the binding props to 1 if the estimated row count of the left side is less than 1. Fixes cockroachdb#49911 Release note (bug fix): Fixed an internal planning error that occured for recursive CTEs (WITH RECURSIVE expressions) in which the left side of the UNION ALL query used in the CTE definition produced zero rows.
Member
|
This change is |
mgartner
approved these changes
Jun 8, 2020
Contributor
mgartner
left a comment
There was a problem hiding this comment.
Reviewed 2 of 2 files at r1.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @RaduBerinde)
Collaborator
Author
|
TFTR! bors r+ |
Contributor
Build succeeded |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Prior to this commit, a recursive CTE in which the cardinality of
the left side of the
UNION ALLexpression was zero would cause anerror in the statistics code, "estimated row count must be non-zero".
This was happening because the cardinality of the recursive CTE binding
props was set to be non-zero, but the row count, which came from the
left side expression, was not updated accordingly. The stats code only
allows the row count to be zero if the cardinality is also zero.
This commit fixes the problem by setting the row count of the binding
props to 1 if the estimated row count of the left side is less than 1.
Fixes #49911
Release note (bug fix): Fixed an internal planning error that occured
for recursive CTEs (WITH RECURSIVE expressions) in which the left side
of the UNION ALL query used in the CTE definition produced zero rows.