[GitHub] [spark] cfmcgrady commented on a change in pull request #33142: [SPARK-35940][SQL] Refactor EquivalentExpressions to make it more efficient

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

cfmcgrady commented on a change in pull request #33142:
URL: https://github.com/apache/spark/pull/33142#discussion_r662909946



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -93,25 +72,33 @@ class EquivalentExpressions {
    */
   private def addCommonExprs(
       exprs: Seq[Expression],
-      addFunc: Expression => Boolean = addExpr): Unit = {
-    val exprSetForAll = mutable.Set[Expr]()
-    addExprTree(exprs.head, addExprToSet(_, exprSetForAll))
-
-    val candidateExprs = exprs.tail.foldLeft(exprSetForAll) { (exprSet, expr) =>
-      val otherExprSet = mutable.Set[Expr]()
-      addExprTree(expr, addExprToSet(_, otherExprSet))
-      exprSet.intersect(otherExprSet)
+      map: mutable.HashMap[ExpressionEquals, ExpressionStats]): Unit = {
+    assert(exprs.length > 1)
+    var localEquivalenceMap = mutable.HashMap.empty[ExpressionEquals, ExpressionStats]

Review comment:
       This also fixed that, previously, for `Or(Coalesce(expr1, expr2, expr2), Coalesce(expr1, expr2, expr2))`, `expr2` will be extracted and considered as common subexpression. Currently, no subexpression will be extracted.




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