englefly opened a new pull request, #65703:
URL: https://github.com/apache/doris/pull/65703
### What problem does this PR solve?
do not push down a scalar agg to join's child
```
t1 (a, b)
(1,10)
(2,20);
SELECT t1.a, SUM(t1.b), t2.c
FROM t1, t2
WHERE t1.a = 999
GROUP BY t1.a, t2.c
```
plan
```
agg(sum(t1.b) groupkey=[t2.c])
->nlj
->filter(a = 999)
->t1
-> t2
```
without eager-agg, the output of nlj is empty, becase all rows of t1 are
filtered.
if we push down agg uppon filter, the agg is scalar agg, since t1.a is
eliminated by constant propagation.
the plan becomes
```
agg1(sum(x) groupkey=[t2.c])
->nlj
-> agg2(sum(t1.b) as x, groupkey=[])
->filter(a = 999)
->t1
-> t2
```
agg2 output at least one row, and hence nlj output is not empty(t2 is not
empty). and the final result is not empty now.
Related PR: #63690
Problem Summary:
### Release note
None
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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