[GitHub] [spark] sigmod commented on a diff in pull request #36121: [SPARK-38836][SQL] Improve the performance of ExpressionSet

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

sigmod commented on code in PR #36121:
URL: https://github.com/apache/spark/pull/36121#discussion_r865439945


##########
sql/catalyst/src/main/scala-2.12/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala:
##########
@@ -74,49 +83,37 @@ class ExpressionSet protected(
 
   protected def remove(e: Expression): Unit = {
     if (e.deterministic) {
-      baseSet --= baseSet.filter(_ == e.canonicalized)
-      originals --= originals.filter(_.canonicalized == e.canonicalized)
+      baseSet.retain(_ != e.canonicalized)

Review Comment:
   how about:
   `baseSet.remove(e.canonicalized)`



##########
sql/catalyst/src/main/scala-2.13/org/apache/spark/sql/catalyst/expressions/ExpressionSet.scala:
##########
@@ -0,0 +1,168 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.expressions
+
+import scala.collection.{mutable, IterableFactory, IterableOps}
+import scala.collection.mutable.ArrayBuffer
+
+object ExpressionSet {
+  /** Constructs a new [[ExpressionSet]] by applying [[Canonicalize]] to `expressions`. */
+  def apply(expressions: IterableOnce[Expression]): ExpressionSet = {
+    val set = new ExpressionSet()
+    expressions.iterator.foreach(set.add)
+    set
+  }
+
+  def apply(): ExpressionSet = {
+    new ExpressionSet()
+  }
+}
+
+/**
+ * A [[Set]] where membership is determined based on determinacy and a canonical representation of
+ * an [[Expression]] (i.e. one that attempts to ignore cosmetic differences).
+ * See [[Canonicalize]] for more details.
+ *
+ * Internally this set uses the canonical representation, but keeps also track of the original
+ * expressions to ease debugging.  Since different expressions can share the same canonical
+ * representation, this means that operations that extract expressions from this set are only
+ * guaranteed to see at least one such expression.  For example:
+ *
+ * {{{
+ *   val set = ExpressionSet(a + 1, 1 + a)
+ *
+ *   set.iterator => Iterator(a + 1)
+ *   set.contains(a + 1) => true
+ *   set.contains(1 + a) => true
+ *   set.contains(a + 2) => false
+ * }}}
+ *
+ * For non-deterministic expressions, they are always considered as not contained in the [[Set]].
+ * On adding a non-deterministic expression, simply append it to the original expressions.
+ * This is consistent with how we define `semanticEquals` between two expressions.
+ *
+ * The constructor of this class is protected so caller can only initialize an Expression from
+ * empty, then build it using `add` and `remove` methods. So every instance of this class holds the
+ * invariant that:
+ * 1. Every expr `e` in `baseSet` satisfies `e.deterministic && e.canonicalized == e`
+ * 2. Every deterministic expr `e` in `originals` satisfies that `e.canonicalized` is already
+ *    accessed.
+ */
+class ExpressionSet protected(
+    private val baseSet: mutable.Set[Expression] = new mutable.HashSet,
+    private var originals: mutable.Buffer[Expression] = new ArrayBuffer)
+  extends scala.collection.Set[Expression]
+    with scala.collection.SetOps[Expression, scala.collection.Set, ExpressionSet] {
+
+  override protected def fromSpecific(coll: IterableOnce[Expression]): ExpressionSet = {
+    val set = new ExpressionSet()
+    coll.iterator.foreach(set.add)
+    set
+  }
+
+  override protected def newSpecificBuilder: mutable.Builder[Expression, ExpressionSet] =
+    new mutable.Builder[Expression, ExpressionSet] {
+      var expr_set: ExpressionSet = new ExpressionSet()
+      def clear(): Unit = expr_set = new ExpressionSet()
+      def result(): ExpressionSet = expr_set
+      def addOne(expr: Expression): this.type = {
+        expr_set.add(expr)
+        this
+      }
+    }
+
+  override def empty: ExpressionSet = new ExpressionSet()
+
+  override def diff(that: scala.collection.Set[Expression]): ExpressionSet = this -- that
+
+  protected def add(e: Expression): Unit = {
+    if (!e.deterministic) {
+      originals += e
+    } else if (!baseSet.contains(e.canonicalized)) {
+      baseSet.add(e.canonicalized)
+      originals += e
+    }
+  }
+
+  protected def remove(e: Expression): Unit = {
+    if (e.deterministic) {
+      baseSet.filterInPlace(_ != e.canonicalized)

Review Comment:
   How about:
   
   `baseSet.remove(e.canonicalized)`



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