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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.execution
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.catalyst.InternalRow
import org.apache.spark.sql.catalyst.errors._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.expressions.codegen._
import org.apache.spark.sql.catalyst.expressions.codegen.Block._
import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, UnknownPartitioning}
import org.apache.spark.sql.execution.metric.SQLMetrics
/**
* Apply all of the GroupExpressions to every input row, hence we will get
* multiple output rows for an input row.
* @param projections The group of expressions, all of the group expressions should
* output the same schema specified bye the parameter `output`
* @param output The output Schema
* @param child Child operator
*/
case class ExpandExec(
projections: Seq[Seq[Expression]],
output: Seq[Attribute],
child: SparkPlan)
extends UnaryExecNode with CodegenSupport {
override lazy val metrics = Map(
"numOutputRows" -> SQLMetrics.createMetric(sparkContext, "number of output rows"))
// The GroupExpressions can output data with arbitrary partitioning, so set it
// as UNKNOWN partitioning
override def outputPartitioning: Partitioning = UnknownPartitioning(0)
@transient
override lazy val references: AttributeSet =
AttributeSet(projections.flatten.flatMap(_.references))
private[this] val projection =
(exprs: Seq[Expression]) => UnsafeProjection.create(exprs, child.output)
protected override def doExecute(): RDD[InternalRow] = attachTree(this, "execute") {
val numOutputRows = longMetric("numOutputRows")
child.execute().mapPartitions { iter =>
val groups = projections.map(projection).toArray
new Iterator[InternalRow] {
private[this] var result: InternalRow = _
private[this] var idx = -1 // -1 means the initial state
private[this] var input: InternalRow = _
override final def hasNext: Boolean = (-1 < idx && idx < groups.length) || iter.hasNext
override final def next(): InternalRow = {
if (idx <= 0) {
// in the initial (-1) or beginning(0) of a new input row, fetch the next input tuple
input = iter.next()
idx = 0
}
result = groups(idx)(input)
idx += 1
if (idx == groups.length && iter.hasNext) {
idx = 0
}
numOutputRows += 1
result
}
}
}
}
override def inputRDDs(): Seq[RDD[InternalRow]] = {
child.asInstanceOf[CodegenSupport].inputRDDs()
}
protected override def doProduce(ctx: CodegenContext): String = {
child.asInstanceOf[CodegenSupport].produce(ctx, this)
}
override def needCopyResult: Boolean = true
override def doConsume(ctx: CodegenContext, input: Seq[ExprCode], row: ExprCode): String = {
/*
* When the projections list looks like:
* expr1A, exprB, expr1C
* expr2A, exprB, expr2C
* ...
* expr(N-1)A, exprB, expr(N-1)C
*
* i.e. column A and C have different values for each output row, but column B stays constant.
*
* The generated code looks something like (note that B is only computed once in declaration):
*
* // part 1: declare all the columns
* colA = ...
* colB = ...
* colC = ...
*
* // part 2: code that computes the columns
* for (row = 0; row < N; row++) {
* switch (row) {
* case 0:
* colA = ...
* colC = ...
* case 1:
* colA = ...
* colC = ...
* ...
* case N - 1:
* colA = ...
* colC = ...
* }
* // increment metrics and consume output values
* }
*
* We use a for loop here so we only includes one copy of the consume code and avoid code
* size explosion.
*/
// Tracks whether a column has the same output for all rows.
// Size of sameOutput array should equal N.
// If sameOutput(i) is true, then the i-th column has the same value for all output rows given
// an input row.
val sameOutput: Array[Boolean] = output.indices.map { colIndex =>
projections.map(p => p(colIndex)).toSet.size == 1
}.toArray
// Part 1: declare variables for each column
// If a column has the same value for all output rows, then we also generate its computation
// right after declaration. Otherwise its value is computed in the part 2.
lazy val attributeSeq: AttributeSeq = child.output
val outputColumns = output.indices.map { col =>
val firstExpr = projections.head(col)
if (sameOutput(col)) {
// This column is the same across all output rows. Just generate code for it here.
BindReferences.bindReference(firstExpr, attributeSeq).genCode(ctx)
} else {
val isNull = ctx.freshName("isNull")
val value = ctx.freshName("value")
val code = code"""
|boolean $isNull = true;
|${CodeGenerator.javaType(firstExpr.dataType)} $value =
| ${CodeGenerator.defaultValue(firstExpr.dataType)};
""".stripMargin
ExprCode(
code,
JavaCode.isNullVariable(isNull),
JavaCode.variable(value, firstExpr.dataType))
}
}
// Part 2: switch/case statements
val cases = projections.zipWithIndex.map { case (exprs, row) =>
var updateCode = ""
for (col <- exprs.indices) {
if (!sameOutput(col)) {
val ev = BindReferences.bindReference(exprs(col), attributeSeq).genCode(ctx)
updateCode +=
s"""
|${ev.code}
|${outputColumns(col).isNull} = ${ev.isNull};
|${outputColumns(col).value} = ${ev.value};
""".stripMargin
}
}
s"""
|case $row:
| ${updateCode.trim}
| break;
""".stripMargin
}
val numOutput = metricTerm(ctx, "numOutputRows")
val i = ctx.freshName("i")
// these column have to declared before the loop.
val evaluate = evaluateVariables(outputColumns)
s"""
|$evaluate
|for (int $i = 0; $i < ${projections.length}; $i ++) {
| switch ($i) {
| ${cases.mkString("\n").trim}
| }
| $numOutput.add(1);
| ${consume(ctx, outputColumns)}
|}
""".stripMargin
}
}
