[SPARK-13404] [SQL] Create variables for input row when it's actually used #11274
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -83,7 +83,10 @@ trait CodegenSupport extends SparkPlan { | |
| this.parent = parent | ||
| ctx.freshNamePrefix = variablePrefix | ||
| waitForSubqueries() | ||
| s""" | ||
| |/*** PRODUCE: ${toCommentSafeString(this.simpleString)} */ | ||
| |${doProduce(ctx)} | ||
| """.stripMargin | ||
| } | ||
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| /** | ||
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@@ -115,6 +118,39 @@ trait CodegenSupport extends SparkPlan { | |
| parent.consumeChild(ctx, this, input, row) | ||
| } | ||
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| /** | ||
| * Returns source code to evaluate all the variables, and clear the code of them, to prevent | ||
| * them to be evaluated twice. | ||
| */ | ||
| protected def evaluateVariables(variables: Seq[ExprCode]): String = { | ||
|
Contributor
There was a problem hiding this comment. Can you update the comment for ExprCode.code to specify what it means when it is empty. |
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| val evaluate = variables.filter(_.code != "").map(_.code.trim).mkString("\n") | ||
| variables.foreach(_.code = "") | ||
| evaluate | ||
| } | ||
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| /** | ||
| * Returns source code to evaluate the variables for required attributes, and clear the code | ||
| * of evaluated variables, to prevent them to be evaluated twice.. | ||
| */ | ||
| protected def evaluateRequiredVariables( | ||
| attributes: Seq[Attribute], | ||
| variables: Seq[ExprCode], | ||
| required: AttributeSet): String = { | ||
| var evaluateVars = "" | ||
| variables.zipWithIndex.foreach { case (ev, i) => | ||
| if (ev.code != "" && required.contains(attributes(i))) { | ||
|
Member
There was a problem hiding this comment. @davies I was just reviewing build warnings, and it flags this line. |
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| evaluateVars += ev.code.trim + "\n" | ||
| ev.code = "" | ||
| } | ||
| } | ||
| evaluateVars | ||
| } | ||
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| /** | ||
| * The subset of inputSet those should be evaluated before this plan. | ||
|
Contributor
There was a problem hiding this comment. I think this is a good place to document how this whole thing works in a couple of sentences. Something describing that we defer attribute access in the generated function. We access all the attributes needed by the operator at the beginning if it was not already referenced earlier in the pipeline. Might also update the commit message with this since this is what most of the patch is about. |
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| */ | ||
| def usedInputs: AttributeSet = references | ||
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| /** | ||
| * Consume the columns generated from it's child, call doConsume() or emit the rows. | ||
|
Contributor
There was a problem hiding this comment. Can you comment what the semantics are if row == null vs not null? |
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| */ | ||
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@@ -124,19 +160,22 @@ trait CodegenSupport extends SparkPlan { | |
| input: Seq[ExprCode], | ||
| row: String = null): String = { | ||
| ctx.freshNamePrefix = variablePrefix | ||
| val inputVars = | ||
| if (row != null) { | ||
| ctx.currentVars = null | ||
| ctx.INPUT_ROW = row | ||
| child.output.zipWithIndex.map { case (attr, i) => | ||
| BoundReference(i, attr.dataType, attr.nullable).gen(ctx) | ||
| } | ||
| } else { | ||
| input | ||
| } | ||
| s""" | ||
| | | ||
| |/*** CONSUME: ${toCommentSafeString(this.simpleString)} */ | ||
| |${evaluateRequiredVariables(child.output, inputVars, usedInputs)} | ||
| |${doConsume(ctx, inputVars)} | ||
| """.stripMargin | ||
| } | ||
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| /** | ||
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@@ -198,13 +237,9 @@ case class InputAdapter(child: SparkPlan) extends LeafNode with CodegenSupport { | |
| ctx.currentVars = null | ||
| val columns = exprs.map(_.gen(ctx)) | ||
| s""" | ||
| | while (!shouldStop() && $input.hasNext()) { | ||
| | InternalRow $row = (InternalRow) $input.next(); | ||
| | ${consume(ctx, columns).trim} | ||
| | } | ||
| """.stripMargin | ||
| } | ||
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@@ -345,10 +380,12 @@ case class WholeStageCodegen(plan: CodegenSupport, children: Seq[SparkPlan]) | |
| val colExprs = output.zipWithIndex.map { case (attr, i) => | ||
| BoundReference(i, attr.dataType, attr.nullable) | ||
| } | ||
| val evaluateInputs = evaluateVariables(input) | ||
| // generate the code to create a UnsafeRow | ||
| ctx.currentVars = input | ||
| val code = GenerateUnsafeProjection.createCode(ctx, colExprs, false) | ||
| s""" | ||
| |$evaluateInputs | ||
| |${code.code.trim} | ||
| |append(${code.value}.copy()); | ||
| """.stripMargin | ||
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Can you add a high level comment that describes the overall framework? I think the important things to include are:
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I was imagining something like:
evaluateAttributes(Seq[Expression]) which evaluates all the attribute refernces in the tree that haven't been. This is kind of similar to what you have below.
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Some variables could be generated in the middle of the plan, for example, aggregate, and join, so we can't always use the references of current plan to determine which expression is used or not. So I have two different functions here, we could pass in the used references to the function below.