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[SPARK-32721][SQL][FOLLOWUP] Simplify if clauses with null and boolean #29603

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[SPARK-32721][SQL][FOLLOWUP] Simplify if clauses with null and boolean #29603

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[SPARK-32721][SQL][FOLLOWUP] Simplify if clauses with null and boolean
sunchao Sep 1, 2020
34e3d38
Minor nit
sunchao Sep 1, 2020
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2 changes: 2 additions & 0 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -465,6 +465,8 @@ object SimplifyConditionals extends Rule[LogicalPlan] with PredicateHelper {
if cond.deterministic && trueValue.semanticEquals(falseValue) => trueValue
case If(cond, l @ Literal(null, _), FalseLiteral) if !cond.nullable => And(cond, l)
case If(cond, l @ Literal(null, _), TrueLiteral) if !cond.nullable => Or(Not(cond), l)
case If(cond, FalseLiteral, l @ Literal(null, _)) if !cond.nullable => And(Not(cond), l)
case If(cond, TrueLiteral, l @ Literal(null, _)) if !cond.nullable => Or(cond, l)
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minor, can we call l as nullLiteral?

      case If(cond, nullLiteral @ Literal(null, _), FalseLiteral) if !cond.nullable => And(cond, nullLiteral)
      case If(cond, nullLiteral @ Literal(null, _), TrueLiteral) if !cond.nullable => Or(Not(cond), nullLiteral)
      case If(cond, FalseLiteral, nullLiteral @ Literal(null, _)) if !cond.nullable => And(Not(cond), nullLiteral)
      case If(cond, TrueLiteral, nullLiteral @ Literal(null, _)) if !cond.nullable => Or(cond, nullLiteral)

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Hmm that will break each of these into two lines which may affect readability, also I think given these are already Literal(null, _), naming the variable to nullLiteral doesn't add much value maybe?


case e @ CaseWhen(branches, elseValue) if branches.exists(x => falseOrNullLiteral(x._1)) =>
// If there are branches that are always false, remove them.
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10 changes: 9 additions & 1 deletion ...yst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/SimplifyConditionalSuite.scala
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Expand Up @@ -166,29 +166,37 @@ class SimplifyConditionalSuite extends PlanTest with ExpressionEvalHelper with P
)
}

test("simplify if when then clause is null and else clause is boolean") {
test("simplify if when one clause is null and another is boolean") {
val p = IsNull('a)
val nullLiteral = Literal(null, BooleanType)
assertEquivalent(If(p, nullLiteral, FalseLiteral), And(p, nullLiteral))
assertEquivalent(If(p, nullLiteral, TrueLiteral), Or(IsNotNull('a), nullLiteral))
assertEquivalent(If(p, FalseLiteral, nullLiteral), And(IsNotNull('a), nullLiteral))
assertEquivalent(If(p, TrueLiteral, nullLiteral), Or(p, nullLiteral))

// the rule should not apply to nullable predicate
Seq(TrueLiteral, FalseLiteral).foreach { b =>
assertEquivalent(If(GreaterThan('a, 42), nullLiteral, b),
If(GreaterThan('a, 42), nullLiteral, b))
assertEquivalent(If(GreaterThan('a, 42), b, nullLiteral),
If(GreaterThan('a, 42), b, nullLiteral))
}

// check evaluation also
Seq(TrueLiteral, FalseLiteral).foreach { b =>
checkEvaluation(If(b, nullLiteral, FalseLiteral), And(b, nullLiteral).eval(EmptyRow))
checkEvaluation(If(b, nullLiteral, TrueLiteral), Or(Not(b), nullLiteral).eval(EmptyRow))
checkEvaluation(If(b, FalseLiteral, nullLiteral), And(Not(b), nullLiteral).eval(EmptyRow))
checkEvaluation(If(b, TrueLiteral, nullLiteral), Or(b, nullLiteral).eval(EmptyRow))
}

// should have no effect on expressions with nullable if condition
assert((Factorial(5) > 100L).nullable)
Seq(TrueLiteral, FalseLiteral).foreach { b =>
checkEvaluation(If(Factorial(5) > 100L, nullLiteral, b),
If(Factorial(5) > 100L, nullLiteral, b).eval(EmptyRow))
checkEvaluation(If(Factorial(5) > 100L, b, nullLiteral),
If(Factorial(5) > 100L, b, nullLiteral).eval(EmptyRow))
}
}
}