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BoundAttribute.scala
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BoundAttribute.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.expressions
import org.apache.spark.Logging
import org.apache.spark.sql.catalyst.errors.attachTree
import org.apache.spark.sql.catalyst.expressions.codegen.{GeneratedExpressionCode, Code, CodeGenContext}
import org.apache.spark.sql.types._
import org.apache.spark.sql.catalyst.trees
/**
* A bound reference points to a specific slot in the input tuple, allowing the actual value
* to be retrieved more efficiently. However, since operations like column pruning can change
* the layout of intermediate tuples, BindReferences should be run after all such transformations.
*/
case class BoundReference(ordinal: Int, dataType: DataType, nullable: Boolean)
extends NamedExpression with trees.LeafNode[Expression] {
override def toString: String = s"input[$ordinal]"
override def eval(input: Row): Any = input(ordinal)
override def name: String = s"i[$ordinal]"
override def toAttribute: Attribute = throw new UnsupportedOperationException
override def qualifiers: Seq[String] = throw new UnsupportedOperationException
override def exprId: ExprId = throw new UnsupportedOperationException
override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): Code = {
s"""
boolean ${ev.isNull} = i.isNullAt($ordinal);
${ctx.primitiveType(dataType)} ${ev.primitive} = ${ev.isNull} ?
${ctx.defaultValue(dataType)} : (${ctx.getColumn(dataType, ordinal)});
"""
}
}
object BindReferences extends Logging {
def bindReference[A <: Expression](
expression: A,
input: Seq[Attribute],
allowFailures: Boolean = false): A = {
expression.transform { case a: AttributeReference =>
attachTree(a, "Binding attribute") {
val ordinal = input.indexWhere(_.exprId == a.exprId)
if (ordinal == -1) {
if (allowFailures) {
a
} else {
sys.error(s"Couldn't find $a in ${input.mkString("[", ",", "]")}")
}
} else {
BoundReference(ordinal, a.dataType, a.nullable)
}
}
}.asInstanceOf[A] // Kind of a hack, but safe. TODO: Tighten return type when possible.
}
}