cloud-fan commented on a change in pull request #30341: URL: https://github.com/apache/spark/pull/30341#discussion_r523962907
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SubExprEvaluationRuntime.scala ########## @@ -0,0 +1,126 @@ +/* + * 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 + +import com.google.common.cache.{CacheBuilder, CacheLoader, LoadingCache} +import com.google.common.util.concurrent.{ExecutionError, UncheckedExecutionException} + +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, ExprCode} +import org.apache.spark.sql.types.DataType + +/** + * This class helps subexpression elimination for interpreted evaluation + * such as `InterpretedUnsafeProjection`. It maintains an evaluation cache. + * This class wraps `ExpressionProxy` around given expressions. The `ExpressionProxy` + * intercepts expression evaluation and loads from the cache first. + */ +class SubExprEvaluationRuntime(cacheMaxEntries: Int) { + + private[sql] val cache: LoadingCache[ExpressionProxy, ResultProxy] = CacheBuilder.newBuilder() + .maximumSize(cacheMaxEntries) + .build( + new CacheLoader[ExpressionProxy, ResultProxy]() { + override def load(expr: ExpressionProxy): ResultProxy = { + ResultProxy(expr.proxyEval(currentInput)) + } + }) + + private var currentInput: InternalRow = null + + def getEval(proxy: ExpressionProxy): Any = try { + cache.get(proxy).result + } catch { + // Cache.get() may wrap the original exception. See the following URL + // http://google.github.io/guava/releases/14.0/api/docs/com/google/common/cache/ + // Cache.html#get(K,%20java.util.concurrent.Callable) + case e @ (_: UncheckedExecutionException | _: ExecutionError) => + throw e.getCause + } + + /** + * Sets given input row as current row for evaluating expressions. This cleans up the cache + * too as new input comes. + */ + def setInput(input: InternalRow = null): Unit = { + currentInput = input + cache.invalidateAll() + } + + /** + * Recursively replaces expression with its proxy expression in `proxyMap`. + */ + private def replaceWithProxy( + expr: Expression, + proxyMap: Map[Expression, ExpressionProxy]): Expression = { + proxyMap.getOrElse(expr, expr.mapChildren(replaceWithProxy(_, proxyMap))) + } + + /** + * Finds subexpressions and wraps them with `ExpressionProxy`. + */ + def proxyExpressions(expressions: Seq[Expression]): Seq[Expression] = { + val equivalentExpressions: EquivalentExpressions = new EquivalentExpressions + + expressions.foreach(equivalentExpressions.addExprTree(_)) + + val proxyMap = mutable.Map.empty[Expression, ExpressionProxy] + + val commonExprs = equivalentExpressions.getAllEquivalentExprs.filter(_.size > 1) + commonExprs.foreach { e => + val expr = e.head + val proxy = ExpressionProxy(expr, this) + + proxyMap ++= e.map(_ -> proxy).toMap + } + + // Only adding proxy if we find subexpressions. + if (proxyMap.nonEmpty) { + expressions.map(replaceWithProxy(_, proxyMap.toMap)) + } else { + expressions + } + } +} + +/** + * A proxy for an catalyst `Expression`. Given a runtime object `SubExprEvaluationRuntime`, + * when this is asked to evaluate, it will load from the evaluation cache in the runtime first. + */ +case class ExpressionProxy( Review comment: for https://github.com/apache/spark/pull/30341#discussion_r523299091 We can define `ExpressionProxy` as `case class ExpressionProxy(child: Expression, id: Int, ...)` and override `equals`/`hashCode`. ---------------------------------------------------------------- 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: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org
