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

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

cloud-fan commented on a change in pull request #33142:
URL: https://github.com/apache/spark/pull/33142#discussion_r660897248



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -93,25 +72,36 @@ 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]
+    addExprTree0(exprs.head, localEquivalenceMap)
+
+    exprs.tail.foreach { expr =>
+      val otherLocalEquivalenceMap = mutable.HashMap.empty[ExpressionEquals, ExpressionStats]
+      addExprTree0(expr, otherLocalEquivalenceMap)
+      localEquivalenceMap = localEquivalenceMap.filter { case (key, _) =>
+        otherLocalEquivalenceMap.contains(key)
+      }
     }
 
-    // Not all expressions in the set should be added. We should filter out the related
-    // children nodes.
-    val commonExprSet = candidateExprs.filter { candidateExpr =>
-      candidateExprs.forall { expr =>
-        expr == candidateExpr || expr.e.find(_.semanticEquals(candidateExpr.e)).isEmpty
+    localEquivalenceMap.foreach { case (commonExpr, state) =>
+      val possibleParents = localEquivalenceMap.filter { case (_, v) => v.height > state.height }

Review comment:
       This partially solves the perf issue mentioned in https://github.com/apache/spark/pull/32559/files#r633488455
   
   By filtering with height first, we can reduce the data to iterate. 




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