cloud-fan commented on code in PR #38626:
URL: https://github.com/apache/spark/pull/38626#discussion_r1021042274
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sql/core/src/main/scala/org/apache/spark/sql/execution/SparkOptimizer.scala:
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@@ -51,8 +51,10 @@ class SparkOptimizer(
Batch("Optimize Metadata Only Query", Once,
OptimizeMetadataOnlyQuery(catalog)) :+
Batch("PartitionPruning", Once,
PartitionPruning,
- RowLevelOperationRuntimeGroupFiltering,
- OptimizeSubqueries) :+
+ // We can't run `OptimizeSubqueries` in this batch, as it will optimize
the subqueries
+ // twice which may break some optimizer rules that can only be applied
once. The rule below
+ // only invokes `OptimizeSubqueries` to optimize newly added subqueries.
Review Comment:
All the optimizer batches are optimizing the same query plan. If
`OptimizeSubqueries` appears twice, it means the subqueries are optimized twice.
Note that, most optimizer rules don't optimize subqueries, they need
`OptimizeSubqueries` to invoke the entire optimizer to optimize subqueries
recursively.
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