From 01a7d33d0851d82fd1bb477a58d9925fe8d727d8 Mon Sep 17 00:00:00 2001
From: Wenchen Fan <wenchen@databricks.com>
Date: Mon, 5 Dec 2016 11:37:13 -0800
Subject: [PATCH] [SPARK-18711][SQL] should disable subexpression elimination
for LambdaVariable
## What changes were proposed in this pull request?
This is kind of a long-standing bug, it's hidden until https://github.com/apache/spark/pull/15780 , which may add `AssertNotNull` on top of `LambdaVariable` and thus enables subexpression elimination.
However, subexpression elimination will evaluate the common expressions at the beginning, which is invalid for `LambdaVariable`. `LambdaVariable` usually represents loop variable, which can't be evaluated ahead of the loop.
This PR skips expressions containing `LambdaVariable` when doing subexpression elimination.
## How was this patch tested?
updated test in `DatasetAggregatorSuite`
Author: Wenchen Fan <wenchen@databricks.com>
Closes #16143 from cloud-fan/aggregator.
---
.../sql/catalyst/expressions/EquivalentExpressions.scala | 6 +++++-
.../org/apache/spark/sql/DatasetAggregatorSuite.scala | 8 ++++----
2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
index b8e2b67b2f..6c246a5663 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
@@ -20,6 +20,7 @@ package org.apache.spark.sql.catalyst.expressions
import scala.collection.mutable
import org.apache.spark.sql.catalyst.expressions.codegen.CodegenFallback
+import org.apache.spark.sql.catalyst.expressions.objects.LambdaVariable
/**
* This class is used to compute equality of (sub)expression trees. Expressions can be added
@@ -72,7 +73,10 @@ class EquivalentExpressions {
root: Expression,
ignoreLeaf: Boolean = true,
skipReferenceToExpressions: Boolean = true): Unit = {
- val skip = root.isInstanceOf[LeafExpression] && ignoreLeaf
+ val skip = (root.isInstanceOf[LeafExpression] && ignoreLeaf) ||
+ // `LambdaVariable` is usually used as a loop variable, which can't be evaluated ahead of the
+ // loop. So we can't evaluate sub-expressions containing `LambdaVariable` at the beginning.
+ root.find(_.isInstanceOf[LambdaVariable]).isDefined
// There are some special expressions that we should not recurse into children.
// 1. CodegenFallback: it's children will not be used to generate code (call eval() instead)
// 2. ReferenceToExpressions: it's kind of an explicit sub-expression elimination.
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DatasetAggregatorSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DatasetAggregatorSuite.scala
index 36b2651e5a..0e7eaa9e88 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DatasetAggregatorSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DatasetAggregatorSuite.scala
@@ -92,13 +92,13 @@ object NameAgg extends Aggregator[AggData, String, String] {
}
-object SeqAgg extends Aggregator[AggData, Seq[Int], Seq[Int]] {
+object SeqAgg extends Aggregator[AggData, Seq[Int], Seq[(Int, Int)]] {
def zero: Seq[Int] = Nil
def reduce(b: Seq[Int], a: AggData): Seq[Int] = a.a +: b
def merge(b1: Seq[Int], b2: Seq[Int]): Seq[Int] = b1 ++ b2
- def finish(r: Seq[Int]): Seq[Int] = r
+ def finish(r: Seq[Int]): Seq[(Int, Int)] = r.map(i => i -> i)
override def bufferEncoder: Encoder[Seq[Int]] = ExpressionEncoder()
- override def outputEncoder: Encoder[Seq[Int]] = ExpressionEncoder()
+ override def outputEncoder: Encoder[Seq[(Int, Int)]] = ExpressionEncoder()
}
@@ -281,7 +281,7 @@ class DatasetAggregatorSuite extends QueryTest with SharedSQLContext {
checkDataset(
ds.groupByKey(_.b).agg(SeqAgg.toColumn),
- "a" -> Seq(1, 2)
+ "a" -> Seq(1 -> 1, 2 -> 2)
)
}
--
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