[GitHub] spark pull request #21106: [SPARK-23711][SQL][WIP] Add fallback logic for Un...

[viirya <gi...@git.apache.org>]

Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/21106#discussion_r186305770
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/CodegenObjectFactory.scala ---
    @@ -0,0 +1,66 @@
    +/*
    + * 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 org.codehaus.commons.compiler.CompileException
    +import org.codehaus.janino.InternalCompilerException
    +
    +import org.apache.spark.sql.internal.SQLConf
    +import org.apache.spark.util.Utils
    +
    +/**
    + * Catches compile error during code generation.
    + */
    +object CodegenError {
    +  def unapply(throwable: Throwable): Option[Exception] = throwable match {
    +    case e: InternalCompilerException => Some(e)
    +    case e: CompileException => Some(e)
    +    case _ => None
    +  }
    +}
    +
    +/**
    + * A factory which can be used to create objects that have both codegen and interpreted
    + * implementations. This tries to create codegen object first, if any compile error happens,
    + * it fallbacks to interpreted version.
    + */
    +abstract class CodegenObjectFactory[IN, OUT] {
    +
    +  // Creates wanted object. First trying codegen implementation. If any compile error happens,
    +  // fallbacks to interpreted version.
    +  def createObject(in: IN): OUT = {
    +    val fallbackMode = SQLConf.get.getConf(SQLConf.CODEGEN_OBJECT_FALLBACK)
    --- End diff --
    
    We can only access SQLConf on the driver. We can't know this config value inside `createObject` which can be called on executors. 
    
    To solve this, `UnsafeProjection` can't be an object as now, but a case class with a fallback mode parameter. So we can create this factory on driver. @cloud-fan @hvanhovell WDYT?


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