yaooqinn opened a new pull request, #54135:
URL: https://github.com/apache/spark/pull/54135
### What changes were proposed in this pull request?
This PR adds a new optimizer rule `CrossJoinArrayContainsToInnerJoin` that
converts cross joins with `array_contains` filter into inner joins using
explode/unnest.
**Transformation:**
```
-- Before (O(N×M) cross join):
Filter(array_contains(arr, elem))
CrossJoin(left, right)
-- After (O(N+M) inner join):
InnerJoin(unnested = elem)
Generate(Explode(ArrayDistinct(arr)), left)
right
```
This optimization is ported from Presto's
`CrossJoinWithArrayContainsToInnerJoin` optimizer rule.
### Why are the changes needed?
Queries with `array_contains` in join conditions currently execute as
expensive cross joins with filter. This optimization significantly improves
performance by converting them to efficient inner joins.
**Benchmark Results (10K orders × 1K items):**
| JDK | Unoptimized | Optimized | Speedup |
|-----|-------------|-----------|---------|
| 17 | 504 ms | 45 ms | **11.2X** |
| 21 | 582 ms | 36 ms | **16.1X** |
### Does this PR introduce _any_ user-facing change?
No. This is an internal optimizer improvement that automatically applies to
applicable queries.
### How was this patch tested?
1. **Unit tests:** `CrossJoinArrayContainsToInnerJoinSuite` with 6 test cases
2. **Microbenchmarks:** `CrossJoinArrayContainsToInnerJoinBenchmark` run on
JDK 17 and 21
3. All existing tests pass
### Was this patch authored or co-authored using generative AI tooling?
Yes, GitHub Copilot CLI was used to assist with porting the optimization
from Presto.
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