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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2020/07/16 14:29:13 UTC
[GitHub] [spark] attilapiros commented on a change in pull request #28885: [SPARK-29375][SPARK-28940][SPARK-32041][SQL] Whole plan exchange and subquery reuse
attilapiros commented on a change in pull request #28885:
URL: https://github.com/apache/spark/pull/28885#discussion_r455826311
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/util/ReuseMap.scala
##########
@@ -0,0 +1,73 @@
+/*
+ * 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.util
+
+import scala.collection.mutable.Map
+import scala.language.existentials
+
+import org.apache.spark.sql.catalyst.plans.QueryPlan
+import org.apache.spark.sql.types.StructType
+
+/**
+ * Map of canonicalized plans that can be used to find reuse possibilities.
+ *
+ * To avoid costly canonicalization of a plan:
+ * - we use its schema first to check if it can be replaced to a reused one at all
+ * - we insert it into the map of canonicalized plans only when at least 2 have the same schema
+ */
+class ReuseMap[T <: QueryPlan[_]] {
+ // scalastyle:off structural.type
+ private val map = Map[StructType, (T, Map[T2 forSome { type T2 >: T }, T])]()
+ // scalastyle:on structural.type
+
+ /**
+ * Find a matching plan with the same canonicalized form in the map or add the new plan to the
+ * map otherwise.
+ *
+ * @param plan the input plan
+ * @return the matching plan or the input plan
+ */
+ def lookupOrElseAdd(plan: T): T = {
+ val (firstSameSchemaPlan, sameResultPlans) = map.getOrElseUpdate(plan.schema, plan -> Map())
+ if (firstSameSchemaPlan ne plan) {
+ if (sameResultPlans.isEmpty) {
+ sameResultPlans += firstSameSchemaPlan.canonicalized -> firstSameSchemaPlan
Review comment:
Could you please add more comments here.
Now I understand the `firstSameSchemaPlan` is also needed to be canonicalized but only when the `schema` reappears in multiple times but to get this I needed some offline help from you :)
And again thanks for explaining me this part!
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/util/ReuseMap.scala
##########
@@ -0,0 +1,73 @@
+/*
+ * 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.util
+
+import scala.collection.mutable.Map
+import scala.language.existentials
+
+import org.apache.spark.sql.catalyst.plans.QueryPlan
+import org.apache.spark.sql.types.StructType
+
+/**
+ * Map of canonicalized plans that can be used to find reuse possibilities.
+ *
+ * To avoid costly canonicalization of a plan:
+ * - we use its schema first to check if it can be replaced to a reused one at all
+ * - we insert it into the map of canonicalized plans only when at least 2 have the same schema
+ */
+class ReuseMap[T <: QueryPlan[_]] {
+ // scalastyle:off structural.type
+ private val map = Map[StructType, (T, Map[T2 forSome { type T2 >: T }, T])]()
+ // scalastyle:on structural.type
+
+ /**
+ * Find a matching plan with the same canonicalized form in the map or add the new plan to the
+ * map otherwise.
+ *
+ * @param plan the input plan
+ * @return the matching plan or the input plan
+ */
+ def lookupOrElseAdd(plan: T): T = {
+ val (firstSameSchemaPlan, sameResultPlans) = map.getOrElseUpdate(plan.schema, plan -> Map())
+ if (firstSameSchemaPlan ne plan) {
+ if (sameResultPlans.isEmpty) {
+ sameResultPlans += firstSameSchemaPlan.canonicalized -> firstSameSchemaPlan
+ }
+ sameResultPlans.getOrElseUpdate(plan.canonicalized, plan)
+ } else {
+ plan
+ }
+ }
+
+ /**
+ * Find a matching plan with the same canonicalized form in the map and apply `f` on it or add
+ * the new plan to the map otherwise.
+ *
+ * @param plan the input plan
+ * @param f the function to apply
+ * @return the matching plan with `f` applied or the input plan
+ */
+ def reuseOrElseAdd[T2 >: T](plan: T, f: T => T2): T2 = {
Review comment:
Nit: this might be a better name `transformReusedOrAdd` and/or consider rename `f` to `funcOnReused`. What do you think?
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/util/ReuseMap.scala
##########
@@ -0,0 +1,73 @@
+/*
+ * 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.util
+
+import scala.collection.mutable.Map
+import scala.language.existentials
+
+import org.apache.spark.sql.catalyst.plans.QueryPlan
+import org.apache.spark.sql.types.StructType
+
+/**
+ * Map of canonicalized plans that can be used to find reuse possibilities.
+ *
+ * To avoid costly canonicalization of a plan:
+ * - we use its schema first to check if it can be replaced to a reused one at all
+ * - we insert it into the map of canonicalized plans only when at least 2 have the same schema
+ */
+class ReuseMap[T <: QueryPlan[_]] {
+ // scalastyle:off structural.type
+ private val map = Map[StructType, (T, Map[T2 forSome { type T2 >: T }, T])]()
+ // scalastyle:on structural.type
+
+ /**
+ * Find a matching plan with the same canonicalized form in the map or add the new plan to the
+ * map otherwise.
+ *
+ * @param plan the input plan
+ * @return the matching plan or the input plan
+ */
+ def lookupOrElseAdd(plan: T): T = {
+ val (firstSameSchemaPlan, sameResultPlans) = map.getOrElseUpdate(plan.schema, plan -> Map())
+ if (firstSameSchemaPlan ne plan) {
Review comment:
Nit: Is this reference check needed only for the `getOrElseUpdate`? I might go for to use a simple `get` and handle the `None` by adding the `plan -> Map()`
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