[GitHub] [spark] mgaido91 commented on a change in pull request #23942: [SPARK-27033][SQL]Add Optimize rule RewriteArithmeticFiltersOnIntOrLongColumn

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mgaido91 commented on a change in pull request #23942: [SPARK-27033][SQL]Add Optimize rule RewriteArithmeticFiltersOnIntOrLongColumn
URL: https://github.com/apache/spark/pull/23942#discussion_r263021516
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteArithmeticFiltersOnIntOrLongColumn.scala
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+/*
+ * 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._
+import org.apache.spark.sql.catalyst.plans.logical.{Filter, LogicalPlan}
+import org.apache.spark.sql.catalyst.rules.Rule
+import org.apache.spark.sql.types.{DataType, IntegerType, LongType}
+
+/**
+ * Rewrite arithmetic filters on int or long column to its equivalent form,
+ * leaving attribute alone in one side, so that we can push it down to
+ * parquet or other file format.
+ * For example, this rule can optimize
+ * {{{
+ *   SELECT * FROM table WHERE i + 3 = 5
+ * }}}
+ * to
+ * {{{
+ *   SELECT * FROM table WHERE i = 5 - 3
+ * }}}
+ * when i is Int or Long, and then other rules will further optimize it to
+ * {{{
+ *   SELECT * FROM table WHERE i = 2
+ * }}}
+ * The arithmetic operation supports `Add` and `Subtract`. The comparision supports
+ * '=', '>=', '<=', '>', '<', '!='. It only supports type of `INT` and `LONG`,
+ * it doesn't support `FLOAT` or `DOUBLE` for precision issues.
+ */
+object RewriteArithmeticFiltersOnIntOrLongColumn extends Rule[LogicalPlan] with PredicateHelper {
+  def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+    case f: Filter =>
+      f transformExpressionsUp {
+        case e @ BinaryComparison(left: BinaryArithmetic, right: Expression)
+            if right.foldable && isDataTypeSafe(left.dataType) =>
+          transformLeft(e, left, right)
+        case e @ BinaryComparison(left: Expression, right: BinaryArithmetic)
+            if left.foldable && isDataTypeSafe(right.dataType) =>
+          transformRight(e, left, right)
+      }
+  }
+
+  private def transformLeft(
+      bc: BinaryComparison,
+      left: BinaryArithmetic,
+      right: Expression): Expression = {
+    left match {
+      case Add(ar: AttributeReference, e) if e.foldable && isOptSafe(Subtract(right, e)) =>
+        bc.makeCopy(Array(ar, Subtract(right, e)))
+      case Add(e, ar: AttributeReference) if e.foldable && isOptSafe(Subtract(right, e)) =>
+        bc.makeCopy(Array(ar, Subtract(right, e)))
+      case Subtract(ar: AttributeReference, e) if e.foldable && isOptSafe(Add(right, e)) =>
+        bc.makeCopy(Array(ar, Add(right, e)))
+      case Subtract(e, ar: AttributeReference) if e.foldable && isOptSafe(Subtract(e, right)) =>
+        bc.makeCopy(Array(Subtract(e, right), ar))
+      case _ => bc
+    }
+  }
+
+  private def transformRight(
+      bc: BinaryComparison,
+      left: Expression,
+      right: BinaryArithmetic): Expression = {
+    right match {
+      case Add(ar: AttributeReference, e) if e.foldable && isOptSafe(Subtract(left, e)) =>
+        bc.makeCopy(Array(Subtract(left, e), ar))
+      case Add(e, ar: AttributeReference) if e.foldable && isOptSafe(Subtract(left, e)) =>
+        bc.makeCopy(Array(Subtract(left, e), ar))
+      case Subtract(ar: AttributeReference, e) if e.foldable && isOptSafe(Add(left, e)) =>
+        bc.makeCopy(Array(Add(left, e), ar))
+      case Subtract(e, ar: AttributeReference) if e.foldable && isOptSafe(Subtract(e, left)) =>
+        bc.makeCopy(Array(ar, Subtract(e, left)))
+      case _ => bc
+    }
+  }
+
+  private def isDataTypeSafe(dataType: DataType): Boolean = dataType match {
 
 Review comment:
   why only integer and longs are accepted?

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