[GitHub] [spark] beliefer commented on a diff in pull request #38799: [SPARK-37099][SQL] Introduce the group limit of Window for rank-based filter to optimize top-k computation

["beliefer (via GitHub)" <gi...@apache.org>]

beliefer commented on code in PR #38799:
URL: https://github.com/apache/spark/pull/38799#discussion_r1100909992


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/InsertWindowGroupLimit.scala:
##########
@@ -0,0 +1,96 @@
+/*
+ * 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.optimizer
+
+import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute, CurrentRow, DenseRank, EqualTo, Expression, GreaterThan, GreaterThanOrEqual, IntegerLiteral, LessThan, LessThanOrEqual, NamedExpression, PredicateHelper, Rank, RowFrame, RowNumber, SpecifiedWindowFrame, UnboundedPreceding, WindowExpression, WindowSpecDefinition}
+import org.apache.spark.sql.catalyst.plans.logical.{Filter, LocalRelation, LogicalPlan, Window, WindowGroupLimit}
+import org.apache.spark.sql.catalyst.rules.Rule
+import org.apache.spark.sql.catalyst.trees.TreePattern.{FILTER, WINDOW}
+
+/**
+ * Optimize the filter based on rank-like window function by reduce not required rows.
+ * This rule optimizes the following cases:
+ * {{{
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE rn = 5
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE 5 = rn
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE rn < 5
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE 5 > rn
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE rn <= 5
+ *   SELECT *, ROW_NUMBER() OVER(PARTITION BY k ORDER BY a) AS rn FROM Tab1 WHERE 5 >= rn
+ * }}}
+ */
+object InsertWindowGroupLimit extends Rule[LogicalPlan] with PredicateHelper {
+
+  /**
+   * Extract all the limit values from predicates.
+   */
+  def extractLimits(condition: Expression, attr: Attribute): Option[Int] = {
+    val limits = splitConjunctivePredicates(condition).collect {
+      case EqualTo(IntegerLiteral(limit), e) if e.semanticEquals(attr) => limit
+      case EqualTo(e, IntegerLiteral(limit)) if e.semanticEquals(attr) => limit
+      case LessThan(e, IntegerLiteral(limit)) if e.semanticEquals(attr) => limit - 1
+      case GreaterThan(IntegerLiteral(limit), e) if e.semanticEquals(attr) => limit - 1
+      case LessThanOrEqual(e, IntegerLiteral(limit)) if e.semanticEquals(attr) => limit
+      case GreaterThanOrEqual(IntegerLiteral(limit), e) if e.semanticEquals(attr) => limit
+    }
+
+    if (limits.nonEmpty) Some(limits.min) else None
+  }
+
+  private def support(
+      windowExpression: NamedExpression): Boolean = windowExpression match {
+    case Alias(WindowExpression(_: Rank | _: DenseRank | _: RowNumber, WindowSpecDefinition(_, _,
+    SpecifiedWindowFrame(RowFrame, UnboundedPreceding, CurrentRow))), _) => true
+    case _ => false
+  }
+
+  def apply(plan: LogicalPlan): LogicalPlan = {
+    if (conf.windowGroupLimitThreshold == -1) return plan
+
+    plan.transformWithPruning(_.containsAllPatterns(FILTER, WINDOW), ruleId) {
+      case filter @ Filter(condition,
+        window @ Window(windowExpressions, partitionSpec, orderSpec, child))
+        if !child.isInstanceOf[WindowGroupLimit] && windowExpressions.exists(support) &&
+          orderSpec.nonEmpty =>
+        val limits = windowExpressions.collect {
+          case alias @ Alias(WindowExpression(rankLikeFunction, _), _) if support(alias) =>
+            extractLimits(condition, alias.toAttribute).map((_, rankLikeFunction))
+        }.flatten
+
+        // multiple different rank-like functions unsupported.
+        if (limits.isEmpty) {
+          filter
+        } else {
+          limits.minBy(_._1) match {

Review Comment:
   Good idea.



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