spark-instrumented-optimizer/sql/core
Wenchen Fan 859a53424a [SPARK-35447][SQL] Optimize skew join before coalescing shuffle partitions
### What changes were proposed in this pull request?

This PR improves the interaction between partition coalescing and skew handling by moving the skew join rule ahead of the partition coalescing rule and making corresponding changes to the two rules:
1. Simplify `OptimizeSkewedJoin` as it doesn't need to handle `CustomShuffleReaderExec` anymore.
2. Update `CoalesceShufflePartitions` to support coalescing non-skewed partitions.

### Why are the changes needed?

It's a bit hard to reason about skew join if partitions have been coalesced. A skewed partition needs to be much larger than other partitions and we need to look at the raw sizes before coalescing.

It also makes `OptimizeSkewedJoin` more robust, as we don't need to worry about a skewed partition being coalesced with a small partition and breaks skew join handling.

It also helps with https://github.com/apache/spark/pull/31653 , which needs to move `OptimizeSkewedJoin` to an earlier phase and run before `CoalesceShufflePartitions`.

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

new UT and existing tests

Closes #32594 from cloud-fan/shuffle.

Lead-authored-by: Wenchen Fan <wenchen@databricks.com>
Co-authored-by: Wenchen Fan <cloud0fan@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
2021-05-25 13:12:45 +00:00
..
benchmarks [SPARK-34981][SQL][FOLLOWUP] Use SpecificInternalRow in ApplyFunctionExpression 2021-05-24 17:25:24 +09:00
src [SPARK-35447][SQL] Optimize skew join before coalescing shuffle partitions 2021-05-25 13:12:45 +00:00
pom.xml [SPARK-33662][BUILD] Setting version to 3.2.0-SNAPSHOT 2020-12-04 14:10:42 -08:00