[GitHub] [spark] dongjoon-hyun commented on a change in pull request #30245: [SPARK-33337][SQL] Support subexpression elimination in branches of conditional expressions

[GitBox <gi...@apache.org>]

dongjoon-hyun commented on a change in pull request #30245:
URL: https://github.com/apache/spark/pull/30245#discussion_r518408688



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
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@@ -65,11 +65,46 @@ class EquivalentExpressions {
     }
   }
 
+  /**
+   * Adds only expressions which are common in each of given expressions, in a recursive way.
+   * For example, given two expressions `(a + (b + (c + 1)))` and `(d + (e + (c + 1)))`,
+   * the common expression `(c + 1)` will be added into `equivalenceMap`.
+   */
+  def addCommonExprs(exprs: Seq[Expression], addFunc: Expression => Boolean = addExpr): Unit = {

Review comment:
       To reduce the SET expression, is it better to exclude non-deterministic expression like `addExpr` function?




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