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

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

cloud-fan commented on a change in pull request #30245:
URL: https://github.com/apache/spark/pull/30245#discussion_r519681590



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -65,11 +65,66 @@ 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 = {
+    var exprSetForAll = ExpressionSet()
+
+    addExprTree(exprs.head, (expr: Expression) => {
+      if (expr.deterministic) {
+        if (exprSetForAll.contains(expr)) {
+          true
+        } else {
+          exprSetForAll += expr
+          false
+        }
+      } else {
+        false
+      }
+    })
+
+    exprs.tail.foreach { expr =>
+      var exprSet = ExpressionSet()
+      addExprTree(expr, (expr: Expression) => {
+        if (expr.deterministic) {
+          if (exprSet.contains(expr)) {
+            true
+          } else {
+            exprSet += expr
+            false
+          }
+        } else {
+          false
+        }
+      })
+      exprSetForAll = exprSetForAll.intersect(exprSet)
+    }
+
+    exprSetForAll.foreach(addFunc)
+  }
+
+  // For some special expressions we cannot just recurse into all of its children, but we can
+  // recursively add the common expressions shared between all of its children.
+  def commonChildrenToRecurse(expr: Expression): Seq[Seq[Expression]] = expr match {

Review comment:
       nit: private




----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org



---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org