Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/993#discussion_r15333352
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala
---
@@ -0,0 +1,458 @@
+/*
+ * 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.codegen
+
+import com.google.common.cache.{CacheLoader, CacheBuilder}
+
+import scala.language.existentials
+
+import org.apache.spark.Logging
+import org.apache.spark.sql.catalyst.expressions
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.types._
+
+/**
+ * A base class for generators of byte code to perform expression
evaluation. Includes a set of
+ * helpers for referring to Catalyst types and building trees that perform
evaluation of individual
+ * expressions.
+ */
+abstract class CodeGenerator[InType <: AnyRef, OutType <: AnyRef] extends
Logging {
+ import scala.reflect.runtime.{universe => ru}
+ import scala.reflect.runtime.universe._
+
+ import scala.tools.reflect.ToolBox
+
+ protected val toolBox =
runtimeMirror(getClass.getClassLoader).mkToolBox()
+
+ protected val rowType = typeOf[Row]
+ protected val mutableRowType = typeOf[MutableRow]
+ protected val genericRowType = typeOf[GenericRow]
+ protected val genericMutableRowType = typeOf[GenericMutableRow]
+
+ protected val projectionType = typeOf[Projection]
+ protected val mutableProjectionType = typeOf[MutableProjection]
+
+ private val curId = new java.util.concurrent.atomic.AtomicInteger()
+ private val javaSeparator = "$"
+
+ /**
+ * Generates a class for a given input expression. Called when there is
not cached code
+ * already available.
+ */
+ protected def create(in: InType): OutType
+
+ /**
+ * Canonicalizes an input expression. Used to avoid double caching
expressions that differ only
+ * cosmetically.
+ */
+ protected def canonicalize(in: InType): InType
+
+ /** Binds an input expression to a given input schema */
+ protected def bind(in: InType, inputSchema: Seq[Attribute]): InType
+
+ protected val cache = CacheBuilder.newBuilder()
+ .maximumSize(1000)
+ .build(
+ new CacheLoader[InType, OutType]() {
+ override def load(in: InType): OutType = globalLock.synchronized {
+ create(in)
+ }
+ })
+
+ def apply(expressions: InType, inputSchema: Seq[Attribute]): OutType=
+ apply(bind(expressions, inputSchema))
+
+ def apply(expressions: InType): OutType =
cache.get(canonicalize(expressions))
+
+ /**
+ * Returns a term name that is unique within this instance of a
`CodeGenerator`.
+ *
+ * (Since we aren't in a macro context we do not seem to have access to
the built in `freshName`
+ * function.)
+ */
+ protected def freshName(prefix: String): TermName = {
+ newTermName(s"$prefix$javaSeparator${curId.getAndIncrement}")
+ }
+
+ /**
+ * Scala ASTs for evaluating an [[Expression]] given a [[Row]] of input.
+ *
+ * @param code The sequence of statements required to evaluate the
expression.
+ * @param nullTerm A term that holds a boolean value representing
whether the expression evaluated
+ * to null.
+ * @param primitiveTerm A term for a possible primitive value of the
result of the evaluation. Not
+ * valid if `nullTerm` is set to `false`.
+ * @param objectTerm A possibly boxed version of the result of
evaluating this expression.
+ */
+ protected case class EvaluatedExpression(
+ code: Seq[Tree],
+ nullTerm: TermName,
+ primitiveTerm: TermName,
+ objectTerm: TermName)
+
+ /**
+ * Given an expression tree returns an [[EvaluatedExpression]], which
contains Scala trees that
+ * can be used to determine the result of evaluating the expression on
an input row.
+ */
+ def expressionEvaluator(e: Expression): EvaluatedExpression = {
+ val primitiveTerm = freshName("primitiveTerm")
+ val nullTerm = freshName("nullTerm")
+ val objectTerm = freshName("objectTerm")
+
+ implicit class Evaluate1(e: Expression) {
+ def castOrNull(f: TermName => Tree, dataType: DataType): Seq[Tree] =
{
+ val eval = expressionEvaluator(e)
+ eval.code ++
+ q"""
+ val $nullTerm = ${eval.nullTerm}
+ val $primitiveTerm =
+ if($nullTerm)
+ ${defaultPrimitive(dataType)}
+ else
+ ${f(eval.primitiveTerm)}
+ """.children
+ }
+ }
+
+ implicit class Evaluate2(expressions: (Expression, Expression)) {
+
+ /**
+ * Short hand for generating binary evaluation code, which depends
on two sub-evaluations of
+ * the same type. If either of the sub-expressions is null, the
result of this computation
+ * is assumed to be null.
+ *
+ * @param f a function from two primitive term names to a tree that
evaluates them.
+ */
+ def evaluate(f: (TermName, TermName) => Tree): Seq[Tree] =
+ evaluateAs(expressions._1.dataType)(f)
+
+ def evaluateAs(resultType: DataType)(f: (TermName, TermName) =>
Tree): Seq[Tree] = {
+ // TODO: Right now some timestamp tests fail if we enforce this...
+ if (expressions._1.dataType != expressions._2.dataType) {
+ log.warn(s"${expressions._1.dataType} !=
${expressions._2.dataType}")
+ }
+
+ val eval1 = expressionEvaluator(expressions._1)
+ val eval2 = expressionEvaluator(expressions._2)
+ val resultCode = f(eval1.primitiveTerm, eval2.primitiveTerm)
+
+ eval1.code ++ eval2.code ++
+ q"""
+ val $nullTerm = ${eval1.nullTerm} || ${eval2.nullTerm}
+ val $primitiveTerm: ${termForType(resultType)} =
+ if($nullTerm) {
+ ${defaultPrimitive(resultType)}
+ } else {
+ $resultCode.asInstanceOf[${termForType(resultType)}]
+ }
+ """.children : Seq[Tree]
+ }
+ }
+
+ val inputTuple = newTermName(s"i")
+
+ // TODO: Skip generation of null handling code when expression are not
nullable.
+ val primitiveEvaluation: PartialFunction[Expression, Seq[Tree]] = {
+ case b @ BoundReference(ordinal, dataType, nullable) =>
+ val nullValue = q"$inputTuple.isNullAt($ordinal)"
+ q"""
+ val $nullTerm: Boolean = $nullValue
+ val $primitiveTerm: ${termForType(dataType)} =
+ if($nullTerm)
+ ${defaultPrimitive(dataType)}
+ else
+ ${getColumn(inputTuple, dataType, ordinal)}
+ """.children
+
+ case expressions.Literal(null, dataType) =>
+ q"""
+ val $nullTerm = true
+ val $primitiveTerm: ${termForType(dataType)} =
null.asInstanceOf[${termForType(dataType)}]
+ """.children
+
+ case expressions.Literal(value: Boolean, dataType) =>
+ q"""
+ val $nullTerm = ${value == null}
+ val $primitiveTerm: ${termForType(dataType)} = $value
+ """.children
+
+ case expressions.Literal(value: String, dataType) =>
+ q"""
+ val $nullTerm = ${value == null}
+ val $primitiveTerm: ${termForType(dataType)} = $value
+ """.children
+
+ case expressions.Literal(value: Int, dataType) =>
+ q"""
+ val $nullTerm = ${value == null}
+ val $primitiveTerm: ${termForType(dataType)} = $value
+ """.children
+
+ case expressions.Literal(value: Long, dataType) =>
+ q"""
+ val $nullTerm = ${value == null}
+ val $primitiveTerm: ${termForType(dataType)} = $value
+ """.children
+
+ case Cast(e @ BinaryType(), StringType) =>
+ val eval = expressionEvaluator(e)
+ eval.code ++
+ q"""
+ val $nullTerm = ${eval.nullTerm}
+ val $primitiveTerm =
+ if($nullTerm)
+ ${defaultPrimitive(StringType)}
+ else
+ new String(${eval.primitiveTerm}.asInstanceOf[Array[Byte]])
+ """.children
+
+ case Cast(child @ NumericType(), IntegerType) =>
+ child.castOrNull(c => q"$c.toInt", IntegerType)
+
+ case Cast(child @ NumericType(), LongType) =>
+ child.castOrNull(c => q"$c.toLong", LongType)
+
+ case Cast(child @ NumericType(), DoubleType) =>
+ child.castOrNull(c => q"$c.toDouble", DoubleType)
+
+ case Cast(child @ NumericType(), FloatType) =>
+ child.castOrNull(c => q"$c.toFloat", IntegerType)
+
+ // Special handling required for timestamps in hive test cases.
--- End diff --
can you also explain inline what the problem is
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