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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2022/02/09 18:52:37 UTC
[GitHub] [spark] allisonwang-db opened a new pull request #35469: [SPARK-38155][SQL] Disallow distinct aggregate in lateral subqueries with unsupported predicates
allisonwang-db opened a new pull request #35469:
URL: https://github.com/apache/spark/pull/35469
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### What changes were proposed in this pull request?
This PR blocks lateral subqueries that contain DISTINCT aggregate and correlated non-equality predicates in CheckAnalysis.
### Why are the changes needed?
To avoid incorrect results. `DISTINCT` will be rewritten into Aggregate during the optimization phase and only correlated equality predicates are supported with Aggregate.
Note, we only need to block this pattern for lateral subqueries because 1) Scalar subqueries are either aggregated or can only contain one row, so they will not encounter this issue 2) IN/EXISTS subqueries can potentially have the same issue but it won't impact the results of these subqueries, for example, `SELECT * FROM t1 WHERE c1 IN (SELECT DISTINCT c1 FROM t2 WHERE t1.c1 > t2.c1)`.
### Does this PR introduce _any_ user-facing change?
Yes. Queries with lateral joins that contain DISTINCT aggregate will be blocked:
```sql
SELECT * FROM t1 JOIN LATERAL (SELECT DISTINCT c2 FROM t2 WHERE c1 > t1.c1)
AnalysisException: Correlated column is not allowed in predicate
```
### How was this patch tested?
Unit tests.
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[GitHub] [spark] allisonwang-db commented on pull request #35469: [SPARK-38155][SQL] Disallow distinct aggregate in lateral subqueries with unsupported predicates
Posted by GitBox <gi...@apache.org>.
allisonwang-db commented on pull request #35469:
URL: https://github.com/apache/spark/pull/35469#issuecomment-1036490564
cc @cloud-fan
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[GitHub] [spark] cloud-fan commented on pull request #35469: [SPARK-38155][SQL] Disallow distinct aggregate in lateral subqueries with unsupported predicates
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on pull request #35469:
URL: https://github.com/apache/spark/pull/35469#issuecomment-1047507425
thanks, merging to master!
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[GitHub] [spark] cloud-fan closed pull request #35469: [SPARK-38155][SQL] Disallow distinct aggregate in lateral subqueries with unsupported predicates
Posted by GitBox <gi...@apache.org>.
cloud-fan closed pull request #35469:
URL: https://github.com/apache/spark/pull/35469
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