wangyum commented on a change in pull request #26257: [SPARK-29606][SQL]
Improve EliminateOuterJoin performance
URL: https://github.com/apache/spark/pull/26257#discussion_r347478495
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
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@@ -176,10 +176,16 @@ abstract class UnaryNode extends LogicalPlan {
allConstraints += EqualNullSafe(a.toAttribute, l)
case a @ Alias(e, _) =>
// For every alias in `projectList`, replace the reference in
constraints by its attribute.
- allConstraints ++= allConstraints.map(_ transform {
- case expr: Expression if expr.semanticEquals(e) =>
- a.toAttribute
- })
+ allConstraints ++= allConstraints.map {
+ case e @ EqualNullSafe(l, _: AttributeReference)
+ if !l.isInstanceOf[AttributeReference] => e
Review comment:
For example:
```scala
import org.apache.spark.sql.catalyst.plans.logical.Project
spark.sql("CREATE TABLE IF NOT EXISTS spark_29606(a int, b int, c int) USING
parquet")
spark.sql("SELECT a as a1, b as b1, c as c1, abc as abc1 FROM (SELECT a, b,
c, a + b + c as abc FROM spark_29606) t")
.queryExecution.analyzed.asInstanceOf[Project].validConstraints.toSeq.sortBy(_.toString).foreach(println)
```
`child.constraints` has a constraint: `(((a#5 + b#6) + c#7) <=> abc#0)`:
**Before this PR**. We will replace the reference in constraints by its
attribute. It will generate a lot of constraints. It seems that these
constraints are useless:
**After this PR**: We avoid generating these useless constraints:
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