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[SPARK-14338][SQL] Improve SimplifyConditionals rule to handle null in IF/CASEWHEN #12122

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[SPARK-14338][SQL] Improve SimplifyConditionals rule to handle null in IF/CASEWHEN #12122

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[SPARK-14338][SQL] Improve `SimplifyConditionals` rule to handle `nul…
dongjoon-hyun Apr 1, 2016
2870d4e
Make `private def`.
dongjoon-hyun Apr 2, 2016
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13 changes: 10 additions & 3 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -527,7 +527,7 @@ object LikeSimplification extends Rule[LogicalPlan] {
* Null value propagation from bottom to top of the expression tree.
*/
object NullPropagation extends Rule[LogicalPlan] {
def nonNullLiteral(e: Expression): Boolean = e match {
private def nonNullLiteral(e: Expression): Boolean = e match {
case Literal(null, _) => false
case _ => true
}
Expand Down Expand Up @@ -773,17 +773,24 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
* Simplifies conditional expressions (if / case).
*/
object SimplifyConditionals extends Rule[LogicalPlan] with PredicateHelper {
private def falseOrNullLiteral(e: Expression): Boolean = e match {
case FalseLiteral => true
case Literal(null, _) => true
case _ => false
}

def apply(plan: LogicalPlan): LogicalPlan = plan transform {
case q: LogicalPlan => q transformExpressionsUp {
case If(TrueLiteral, trueValue, _) => trueValue
case If(FalseLiteral, _, falseValue) => falseValue
case If(Literal(null, _), _, falseValue) => falseValue

case e @ CaseWhen(branches, elseValue) if branches.exists(_._1 == FalseLiteral) =>
case e @ CaseWhen(branches, elseValue) if branches.exists(x => falseOrNullLiteral(x._1)) =>
// If there are branches that are always false, remove them.
// If there are no more branches left, just use the else value.
// Note that these two are handled together here in a single case statement because
// otherwise we cannot determine the data type for the elseValue if it is None (i.e. null).
val newBranches = branches.filter(_._1 != FalseLiteral)
val newBranches = branches.filter(x => !falseOrNullLiteral(x._1))
if (newBranches.isEmpty) {
elseValue.getOrElse(Literal.create(null, e.dataType))
} else {
Expand Down
16 changes: 11 additions & 5 deletions ...yst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SimplifyConditionalSuite.scala
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Expand Up @@ -23,7 +23,7 @@ import org.apache.spark.sql.catalyst.expressions.Literal.{FalseLiteral, TrueLite
import org.apache.spark.sql.catalyst.plans.PlanTest
import org.apache.spark.sql.catalyst.plans.logical._
import org.apache.spark.sql.catalyst.rules._
import org.apache.spark.sql.types.IntegerType
import org.apache.spark.sql.types.{IntegerType, NullType}


class SimplifyConditionalSuite extends PlanTest with PredicateHelper {
Expand All @@ -41,6 +41,7 @@ class SimplifyConditionalSuite extends PlanTest with PredicateHelper {
private val trueBranch = (TrueLiteral, Literal(5))
private val normalBranch = (NonFoldableLiteral(true), Literal(10))
private val unreachableBranch = (FalseLiteral, Literal(20))
private val nullBranch = (Literal(null, NullType), Literal(30))

test("simplify if") {
assertEquivalent(
Expand All @@ -50,18 +51,22 @@ class SimplifyConditionalSuite extends PlanTest with PredicateHelper {
assertEquivalent(
If(FalseLiteral, Literal(10), Literal(20)),
Literal(20))

assertEquivalent(
If(Literal(null, NullType), Literal(10), Literal(20)),
Literal(20))
}

test("remove unreachable branches") {
// i.e. removing branches whose conditions are always false
assertEquivalent(
CaseWhen(unreachableBranch :: normalBranch :: unreachableBranch :: Nil, None),
CaseWhen(unreachableBranch :: normalBranch :: unreachableBranch :: nullBranch :: Nil, None),
CaseWhen(normalBranch :: Nil, None))
}

test("remove entire CaseWhen if only the else branch is reachable") {
assertEquivalent(
CaseWhen(unreachableBranch :: unreachableBranch :: Nil, Some(Literal(30))),
CaseWhen(unreachableBranch :: unreachableBranch :: nullBranch :: Nil, Some(Literal(30))),
Literal(30))

assertEquivalent(
Expand All @@ -71,12 +76,13 @@ class SimplifyConditionalSuite extends PlanTest with PredicateHelper {

test("remove entire CaseWhen if the first branch is always true") {
assertEquivalent(
CaseWhen(trueBranch :: normalBranch :: Nil, None),
CaseWhen(trueBranch :: normalBranch :: nullBranch :: Nil, None),
Literal(5))

// Test branch elimination and simplification in combination
assertEquivalent(
CaseWhen(unreachableBranch :: unreachableBranch:: trueBranch :: normalBranch :: Nil, None),
CaseWhen(unreachableBranch :: unreachableBranch :: nullBranch :: trueBranch :: normalBranch
:: Nil, None),
Literal(5))

// Make sure this doesn't trigger if there is a non-foldable branch before the true branch
Expand Down