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[WIP][Spark-SQL] Optimize the Constant Folding for Expression
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Currently, expression does not support the "constant null" well in constant folding.
e.g. Sum(a, 0) actually always produces Literal(0, NumericType) in runtime.

For example:
```
explain select isnull(key+null)  from src;
== Logical Plan ==
Project [HiveGenericUdf#isnull((key#30 + CAST(null, IntegerType))) AS c_0#28]
 MetastoreRelation default, src, None

== Optimized Logical Plan ==
Project [true AS c_0#28]
 MetastoreRelation default, src, None

== Physical Plan ==
Project [true AS c_0#28]
 HiveTableScan [], (MetastoreRelation default, src, None), None
```

I've create a new Optimization rule called NullPropagation for such kind of constant folding.

Author: Cheng Hao <[email protected]>
Author: Michael Armbrust <[email protected]>

Closes apache#482 from chenghao-intel/optimize_constant_folding and squashes the following commits:

2f14b50 [Cheng Hao] Fix code style issues
68b9fad [Cheng Hao] Remove the Literal pattern matching for NullPropagation
29c8166 [Cheng Hao] Update the code for feedback of code review
50444cc [Cheng Hao] Remove the unnecessary null checking
80f9f18 [Cheng Hao] Update the UnitTest for aggregation constant folding
27ea3d7 [Cheng Hao] Fix Constant Folding Bugs & Add More Unittests
b28e03a [Cheng Hao] Merge pull request #1 from marmbrus/pr/482
9ccefdb [Michael Armbrust] Add tests for optimized expression evaluation.
543ef9d [Cheng Hao] fix code style issues
9cf0396 [Cheng Hao] update code according to the code review comment
536c005 [Cheng Hao] Add Exceptional case for constant folding
3c045c7 [Cheng Hao] Optimize the Constant Folding by adding more rules
2645d4f [Cheng Hao] Constant Folding(null propagation)
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@chenghao-intel @rxin
chenghao-intel authored and rxin committed May 7, 2014
1 parent 913a0a9 commit 3eb53bd
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Showing 14 changed files with 1,502 additions and 32 deletions.
22 changes: 11 additions & 11 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala
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Expand Up @@ -114,37 +114,37 @@ package object dsl {
def attr = analysis.UnresolvedAttribute(s)

/** Creates a new AttributeReference of type boolean */
def boolean = AttributeReference(s, BooleanType, nullable = false)()
def boolean = AttributeReference(s, BooleanType, nullable = true)()

/** Creates a new AttributeReference of type byte */
def byte = AttributeReference(s, ByteType, nullable = false)()
def byte = AttributeReference(s, ByteType, nullable = true)()

/** Creates a new AttributeReference of type short */
def short = AttributeReference(s, ShortType, nullable = false)()
def short = AttributeReference(s, ShortType, nullable = true)()

/** Creates a new AttributeReference of type int */
def int = AttributeReference(s, IntegerType, nullable = false)()
def int = AttributeReference(s, IntegerType, nullable = true)()

/** Creates a new AttributeReference of type long */
def long = AttributeReference(s, LongType, nullable = false)()
def long = AttributeReference(s, LongType, nullable = true)()

/** Creates a new AttributeReference of type float */
def float = AttributeReference(s, FloatType, nullable = false)()
def float = AttributeReference(s, FloatType, nullable = true)()

/** Creates a new AttributeReference of type double */
def double = AttributeReference(s, DoubleType, nullable = false)()
def double = AttributeReference(s, DoubleType, nullable = true)()

/** Creates a new AttributeReference of type string */
def string = AttributeReference(s, StringType, nullable = false)()
def string = AttributeReference(s, StringType, nullable = true)()

/** Creates a new AttributeReference of type decimal */
def decimal = AttributeReference(s, DecimalType, nullable = false)()
def decimal = AttributeReference(s, DecimalType, nullable = true)()

/** Creates a new AttributeReference of type timestamp */
def timestamp = AttributeReference(s, TimestampType, nullable = false)()
def timestamp = AttributeReference(s, TimestampType, nullable = true)()

/** Creates a new AttributeReference of type binary */
def binary = AttributeReference(s, BinaryType, nullable = false)()
def binary = AttributeReference(s, BinaryType, nullable = true)()
}

implicit class DslAttribute(a: AttributeReference) {
Expand Down
1 change: 0 additions & 1 deletion sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
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Expand Up @@ -44,7 +44,6 @@ abstract class Expression extends TreeNode[Expression] {
* - A [[expressions.Cast Cast]] or [[expressions.UnaryMinus UnaryMinus]] is foldable if its
* child is foldable.
*/
// TODO: Supporting more foldable expressions. For example, deterministic Hive UDFs.
def foldable: Boolean = false
def nullable: Boolean
def references: Set[Attribute]
Expand Down
6 changes: 5 additions & 1 deletion sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala
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Expand Up @@ -18,6 +18,7 @@
package org.apache.spark.sql.catalyst.expressions

import org.apache.spark.sql.catalyst.errors.TreeNodeException
import org.apache.spark.sql.catalyst.trees

abstract sealed class SortDirection
case object Ascending extends SortDirection
Expand All @@ -27,7 +28,10 @@ case object Descending extends SortDirection
* An expression that can be used to sort a tuple. This class extends expression primarily so that
* transformations over expression will descend into its child.
*/
case class SortOrder(child: Expression, direction: SortDirection) extends UnaryExpression {
case class SortOrder(child: Expression, direction: SortDirection) extends Expression
with trees.UnaryNode[Expression] {

override def references = child.references
override def dataType = child.dataType
override def nullable = child.nullable

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34 changes: 20 additions & 14 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypes.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ case class GetItem(child: Expression, ordinal: Expression) extends Expression {
val children = child :: ordinal :: Nil
/** `Null` is returned for invalid ordinals. */
override def nullable = true
override def foldable = child.foldable && ordinal.foldable
override def references = children.flatMap(_.references).toSet
def dataType = child.dataType match {
case ArrayType(dt) => dt
Expand All @@ -40,23 +41,27 @@ case class GetItem(child: Expression, ordinal: Expression) extends Expression {
override def toString = s"$child[$ordinal]"

override def eval(input: Row): Any = {
if (child.dataType.isInstanceOf[ArrayType]) {
val baseValue = child.eval(input).asInstanceOf[Seq[_]]
val o = ordinal.eval(input).asInstanceOf[Int]
if (baseValue == null) {
null
} else if (o >= baseValue.size || o < 0) {
null
} else {
baseValue(o)
}
val value = child.eval(input)
if (value == null) {
null
} else {
val baseValue = child.eval(input).asInstanceOf[Map[Any, _]]
val key = ordinal.eval(input)
if (baseValue == null) {
if (key == null) {
null
} else {
baseValue.get(key).orNull
if (child.dataType.isInstanceOf[ArrayType]) {
val baseValue = value.asInstanceOf[Seq[_]]
val o = key.asInstanceOf[Int]
if (o >= baseValue.size || o < 0) {
null
} else {
baseValue(o)
}
} else {
val baseValue = value.asInstanceOf[Map[Any, _]]
val key = ordinal.eval(input)
baseValue.get(key).orNull
}
}
}
}
Expand All @@ -69,7 +74,8 @@ case class GetField(child: Expression, fieldName: String) extends UnaryExpressio
type EvaluatedType = Any

def dataType = field.dataType
def nullable = field.nullable
override def nullable = field.nullable
override def foldable = child.foldable

protected def structType = child.dataType match {
case s: StructType => s
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3 changes: 1 addition & 2 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
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Expand Up @@ -65,8 +65,7 @@ abstract class BinaryPredicate extends BinaryExpression with Predicate {
def nullable = left.nullable || right.nullable
}

case class Not(child: Expression) extends Predicate with trees.UnaryNode[Expression] {
def references = child.references
case class Not(child: Expression) extends UnaryExpression with Predicate {
override def foldable = child.foldable
def nullable = child.nullable
override def toString = s"NOT $child"
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67 changes: 67 additions & 0 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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Expand Up @@ -26,6 +26,7 @@ import org.apache.spark.sql.catalyst.types._
object Optimizer extends RuleExecutor[LogicalPlan] {
val batches =
Batch("ConstantFolding", Once,
NullPropagation,
ConstantFolding,
BooleanSimplification,
SimplifyFilters,
Expand Down Expand Up @@ -85,6 +86,72 @@ object ColumnPruning extends Rule[LogicalPlan] {
}
}

/**
* Replaces [[catalyst.expressions.Expression Expressions]] that can be statically evaluated with
* equivalent [[catalyst.expressions.Literal Literal]] values. This rule is more specific with
* Null value propagation from bottom to top of the expression tree.
*/
object NullPropagation extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transform {
case q: LogicalPlan => q transformExpressionsUp {
case e @ Count(Literal(null, _)) => Literal(0, e.dataType)
case e @ Sum(Literal(c, _)) if c == 0 => Literal(0, e.dataType)
case e @ Average(Literal(c, _)) if c == 0 => Literal(0.0, e.dataType)
case e @ IsNull(c) if c.nullable == false => Literal(false, BooleanType)
case e @ IsNotNull(c) if c.nullable == false => Literal(true, BooleanType)
case e @ GetItem(Literal(null, _), _) => Literal(null, e.dataType)
case e @ GetItem(_, Literal(null, _)) => Literal(null, e.dataType)
case e @ GetField(Literal(null, _), _) => Literal(null, e.dataType)
case e @ Coalesce(children) => {
val newChildren = children.filter(c => c match {
case Literal(null, _) => false
case _ => true
})
if (newChildren.length == 0) {
Literal(null, e.dataType)
} else if (newChildren.length == 1) {
newChildren(0)
} else {
Coalesce(newChildren)
}
}
case e @ If(Literal(v, _), trueValue, falseValue) => if (v == true) trueValue else falseValue
case e @ In(Literal(v, _), list) if (list.exists(c => c match {
case Literal(candidate, _) if candidate == v => true
case _ => false
})) => Literal(true, BooleanType)
case e: UnaryMinus => e.child match {
case Literal(null, _) => Literal(null, e.dataType)
case _ => e
}
case e: Cast => e.child match {
case Literal(null, _) => Literal(null, e.dataType)
case _ => e
}
case e: Not => e.child match {
case Literal(null, _) => Literal(null, e.dataType)
case _ => e
}
// Put exceptional cases above if any
case e: BinaryArithmetic => e.children match {
case Literal(null, _) :: right :: Nil => Literal(null, e.dataType)
case left :: Literal(null, _) :: Nil => Literal(null, e.dataType)
case _ => e
}
case e: BinaryComparison => e.children match {
case Literal(null, _) :: right :: Nil => Literal(null, e.dataType)
case left :: Literal(null, _) :: Nil => Literal(null, e.dataType)
case _ => e
}
case e: StringRegexExpression => e.children match {
case Literal(null, _) :: right :: Nil => Literal(null, e.dataType)
case left :: Literal(null, _) :: Nil => Literal(null, e.dataType)
case _ => e
}
}
}
}

/**
* Replaces [[catalyst.expressions.Expression Expressions]] that can be statically evaluated with
* equivalent [[catalyst.expressions.Literal Literal]] values.
Expand Down
115 changes: 112 additions & 3 deletions .../src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala
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Expand Up @@ -108,9 +108,7 @@ class ExpressionEvaluationSuite extends FunSuite {
truthTable.foreach {
case (l,r,answer) =>
val expr = op(Literal(l, BooleanType), Literal(r, BooleanType))
val result = expr.eval(null)
if (result != answer)
fail(s"$expr should not evaluate to $result, expected: $answer")
checkEvaluation(expr, answer)
}
}
}
Expand All @@ -131,6 +129,7 @@ class ExpressionEvaluationSuite extends FunSuite {

test("LIKE literal Regular Expression") {
checkEvaluation(Literal(null, StringType).like("a"), null)
checkEvaluation(Literal("a", StringType).like(Literal(null, StringType)), null)
checkEvaluation(Literal(null, StringType).like(Literal(null, StringType)), null)
checkEvaluation("abdef" like "abdef", true)
checkEvaluation("a_%b" like "a\\__b", true)
Expand Down Expand Up @@ -159,9 +158,14 @@ class ExpressionEvaluationSuite extends FunSuite {
checkEvaluation("abc" like regEx, true, new GenericRow(Array[Any]("a%")))
checkEvaluation("abc" like regEx, false, new GenericRow(Array[Any]("b%")))
checkEvaluation("abc" like regEx, false, new GenericRow(Array[Any]("bc%")))

checkEvaluation(Literal(null, StringType) like regEx, null, new GenericRow(Array[Any]("bc%")))
}

test("RLIKE literal Regular Expression") {
checkEvaluation(Literal(null, StringType) rlike "abdef", null)
checkEvaluation("abdef" rlike Literal(null, StringType), null)
checkEvaluation(Literal(null, StringType) rlike Literal(null, StringType), null)
checkEvaluation("abdef" rlike "abdef", true)
checkEvaluation("abbbbc" rlike "a.*c", true)

Expand Down Expand Up @@ -257,6 +261,8 @@ class ExpressionEvaluationSuite extends FunSuite {
assert(("abcdef" cast DecimalType).nullable === true)
assert(("abcdef" cast DoubleType).nullable === true)
assert(("abcdef" cast FloatType).nullable === true)

checkEvaluation(Cast(Literal(null, IntegerType), ShortType), null)
}

test("timestamp") {
Expand Down Expand Up @@ -287,5 +293,108 @@ class ExpressionEvaluationSuite extends FunSuite {
// A test for higher precision than millis
checkEvaluation(Cast(Cast(0.00000001, TimestampType), DoubleType), 0.00000001)
}

test("null checking") {
val row = new GenericRow(Array[Any]("^Ba*n", null, true, null))
val c1 = 'a.string.at(0)
val c2 = 'a.string.at(1)
val c3 = 'a.boolean.at(2)
val c4 = 'a.boolean.at(3)

checkEvaluation(IsNull(c1), false, row)
checkEvaluation(IsNotNull(c1), true, row)

checkEvaluation(IsNull(c2), true, row)
checkEvaluation(IsNotNull(c2), false, row)

checkEvaluation(IsNull(Literal(1, ShortType)), false)
checkEvaluation(IsNotNull(Literal(1, ShortType)), true)

checkEvaluation(IsNull(Literal(null, ShortType)), true)
checkEvaluation(IsNotNull(Literal(null, ShortType)), false)

checkEvaluation(Coalesce(c1 :: c2 :: Nil), "^Ba*n", row)
checkEvaluation(Coalesce(Literal(null, StringType) :: Nil), null, row)
checkEvaluation(Coalesce(Literal(null, StringType) :: c1 :: c2 :: Nil), "^Ba*n", row)

checkEvaluation(If(c3, Literal("a", StringType), Literal("b", StringType)), "a", row)
checkEvaluation(If(c3, c1, c2), "^Ba*n", row)
checkEvaluation(If(c4, c2, c1), "^Ba*n", row)
checkEvaluation(If(Literal(null, BooleanType), c2, c1), "^Ba*n", row)
checkEvaluation(If(Literal(true, BooleanType), c1, c2), "^Ba*n", row)
checkEvaluation(If(Literal(false, BooleanType), c2, c1), "^Ba*n", row)
checkEvaluation(If(Literal(false, BooleanType),
Literal("a", StringType), Literal("b", StringType)), "b", row)

checkEvaluation(In(c1, c1 :: c2 :: Nil), true, row)
checkEvaluation(In(Literal("^Ba*n", StringType),
Literal("^Ba*n", StringType) :: Nil), true, row)
checkEvaluation(In(Literal("^Ba*n", StringType),
Literal("^Ba*n", StringType) :: c2 :: Nil), true, row)
}

test("complex type") {
val row = new GenericRow(Array[Any](
"^Ba*n", // 0
null.asInstanceOf[String], // 1
new GenericRow(Array[Any]("aa", "bb")), // 2
Map("aa"->"bb"), // 3
Seq("aa", "bb") // 4
))

val typeS = StructType(
StructField("a", StringType, true) :: StructField("b", StringType, true) :: Nil
)
val typeMap = MapType(StringType, StringType)
val typeArray = ArrayType(StringType)

checkEvaluation(GetItem(BoundReference(3, AttributeReference("c", typeMap)()),
Literal("aa")), "bb", row)
checkEvaluation(GetItem(Literal(null, typeMap), Literal("aa")), null, row)
checkEvaluation(GetItem(Literal(null, typeMap), Literal(null, StringType)), null, row)
checkEvaluation(GetItem(BoundReference(3, AttributeReference("c", typeMap)()),
Literal(null, StringType)), null, row)

checkEvaluation(GetItem(BoundReference(4, AttributeReference("c", typeArray)()),
Literal(1)), "bb", row)
checkEvaluation(GetItem(Literal(null, typeArray), Literal(1)), null, row)
checkEvaluation(GetItem(Literal(null, typeArray), Literal(null, IntegerType)), null, row)
checkEvaluation(GetItem(BoundReference(4, AttributeReference("c", typeArray)()),
Literal(null, IntegerType)), null, row)

checkEvaluation(GetField(BoundReference(2, AttributeReference("c", typeS)()), "a"), "aa", row)
checkEvaluation(GetField(Literal(null, typeS), "a"), null, row)
}

test("arithmetic") {
val row = new GenericRow(Array[Any](1, 2, 3, null))
val c1 = 'a.int.at(0)
val c2 = 'a.int.at(1)
val c3 = 'a.int.at(2)
val c4 = 'a.int.at(3)

checkEvaluation(UnaryMinus(c1), -1, row)
checkEvaluation(UnaryMinus(Literal(100, IntegerType)), -100)

checkEvaluation(Add(c1, c4), null, row)
checkEvaluation(Add(c1, c2), 3, row)
checkEvaluation(Add(c1, Literal(null, IntegerType)), null, row)
checkEvaluation(Add(Literal(null, IntegerType), c2), null, row)
checkEvaluation(Add(Literal(null, IntegerType), Literal(null, IntegerType)), null, row)
}

test("BinaryComparison") {
val row = new GenericRow(Array[Any](1, 2, 3, null))
val c1 = 'a.int.at(0)
val c2 = 'a.int.at(1)
val c3 = 'a.int.at(2)
val c4 = 'a.int.at(3)

checkEvaluation(LessThan(c1, c4), null, row)
checkEvaluation(LessThan(c1, c2), true, row)
checkEvaluation(LessThan(c1, Literal(null, IntegerType)), null, row)
checkEvaluation(LessThan(Literal(null, IntegerType), c2), null, row)
checkEvaluation(LessThan(Literal(null, IntegerType), Literal(null, IntegerType)), null, row)
}
}

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