Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/23139#discussion_r236157275
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
---
@@ -736,69 +736,3 @@ object CombineConcats extends Rule[LogicalPlan] {
flattenConcats(concat)
}
}
-
-/**
- * A rule that replaces `Literal(null, _)` with `FalseLiteral` for further
optimizations.
- *
- * This rule applies to conditions in [[Filter]] and [[Join]]. Moreover,
it transforms predicates
- * in all [[If]] expressions as well as branch conditions in all
[[CaseWhen]] expressions.
- *
- * For example, `Filter(Literal(null, _))` is equal to
`Filter(FalseLiteral)`.
- *
- * Another example containing branches is `Filter(If(cond, FalseLiteral,
Literal(null, _)))`;
- * this can be optimized to `Filter(If(cond, FalseLiteral,
FalseLiteral))`, and eventually
- * `Filter(FalseLiteral)`.
- *
- * As this rule is not limited to conditions in [[Filter]] and [[Join]],
arbitrary plans can
- * benefit from it. For example, `Project(If(And(cond, Literal(null)),
Literal(1), Literal(2)))`
- * can be simplified into `Project(Literal(2))`.
- *
- * As a result, many unnecessary computations can be removed in the query
optimization phase.
- */
-object ReplaceNullWithFalseInPredicate extends Rule[LogicalPlan] {
-
- def apply(plan: LogicalPlan): LogicalPlan = plan transform {
- case f @ Filter(cond, _) => f.copy(condition =
replaceNullWithFalse(cond))
- case j @ Join(_, _, _, Some(cond)) => j.copy(condition =
Some(replaceNullWithFalse(cond)))
- case p: LogicalPlan => p transformExpressions {
- case i @ If(pred, _, _) => i.copy(predicate =
replaceNullWithFalse(pred))
- case cw @ CaseWhen(branches, _) =>
- val newBranches = branches.map { case (cond, value) =>
- replaceNullWithFalse(cond) -> value
- }
- cw.copy(branches = newBranches)
- case af @ ArrayFilter(_, lf @ LambdaFunction(func, _, _)) =>
- val newLambda = lf.copy(function = replaceNullWithFalse(func))
- af.copy(function = newLambda)
- case ae @ ArrayExists(_, lf @ LambdaFunction(func, _, _)) =>
- val newLambda = lf.copy(function = replaceNullWithFalse(func))
- ae.copy(function = newLambda)
- case mf @ MapFilter(_, lf @ LambdaFunction(func, _, _)) =>
- val newLambda = lf.copy(function = replaceNullWithFalse(func))
- mf.copy(function = newLambda)
- }
- }
-
- /**
- * Recursively replaces `Literal(null, _)` with `FalseLiteral`.
- *
- * Note that `transformExpressionsDown` can not be used here as we must
stop as soon as we hit
- * an expression that is not [[CaseWhen]], [[If]], [[And]], [[Or]] or
`Literal(null, _)`.
- */
- private def replaceNullWithFalse(e: Expression): Expression = e match {
- case cw: CaseWhen if cw.dataType == BooleanType =>
- val newBranches = cw.branches.map { case (cond, value) =>
- replaceNullWithFalse(cond) -> replaceNullWithFalse(value)
- }
- val newElseValue = cw.elseValue.map(replaceNullWithFalse)
- CaseWhen(newBranches, newElseValue)
- case i @ If(pred, trueVal, falseVal) if i.dataType == BooleanType =>
- If(replaceNullWithFalse(pred), replaceNullWithFalse(trueVal),
replaceNullWithFalse(falseVal))
- case And(left, right) =>
- And(replaceNullWithFalse(left), replaceNullWithFalse(right))
- case Or(left, right) =>
- Or(replaceNullWithFalse(left), replaceNullWithFalse(right))
- case Literal(null, _) => FalseLiteral
--- End diff --
How about this line? What happened if the input data type of `e` is not
Boolean?
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