*: only add default value for final aggregation to fix the aggregate push down (partition) union case (#35443) #35771
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Outdated suggestions cannot be applied.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.
cherry-pick #35443 to release-6.0
You can switch your code base to this Pull Request by using git-extras:
# In tidb repo: git pr https://github.com/pingcap/tidb/pull/35771
After apply modifications, you can push your change to this PR via:
What problem does this PR solve?
Issue Number: close #35295
Problem Summary:
When table
t
is empty, this get empty result:While this get
NULL
:We add
NULL
(default value) to the empty result here:tidb/executor/aggregate.go
Lines 1368 to 1379 in 2de01b4
Whether or not add the
NULL
row depends on some conditions.Note, for this case, the added
NULL
row make the final result wrong:What is changed and how it works?
Only add
NULL
for final aggregation.Otherwise the add
NULL
row operation would be done several times and send a wrongNULL
row to the final aggregation.Check List
Tests
Side effects
Documentation
Release note
Please refer to Release Notes Language Style Guide to write a quality release note.