snuyanzin commented on code in PR #29825:
URL: https://github.com/apache/flink/pull/29825#discussion_r4514146744
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flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/codegen/calls/ScalarOperatorGens.scala:
##########
@@ -1078,49 +1078,68 @@ object ScalarOperatorGens {
def generateIfElse(
ctx: CodeGeneratorContext,
operands: Seq[GeneratedExpression],
- resultType: LogicalType,
- i: Int = 0): GeneratedExpression = {
- // else part
- if (i == operands.size - 1) {
- generateCast(ctx, operands(i), resultType, nullOnFailure = true)
- } else {
- // check that the condition is boolean
- // we do not check for null instead we use the default value
- // thus null is false
- requireBoolean(operands(i))
- val condition = operands(i)
- val trueAction = generateCast(ctx, operands(i + 1), resultType,
nullOnFailure = true)
- val falseAction = generateIfElse(ctx, operands, resultType, i + 2)
+ resultType: LogicalType): GeneratedExpression = {
+ if (operands.size == 1) {
+ return generateCast(ctx, operands.head, resultType, nullOnFailure = true)
+ }
+ val Seq(resultTerm, nullTerm) = newNames(ctx, "result", "isNull")
+ val resultTypeTerm = primitiveTypeTermForType(resultType)
+ val defaultValue = primitiveDefaultValue(resultType)
- val Seq(resultTerm, nullTerm) = newNames(ctx, "result", "isNull")
- val resultTypeTerm = primitiveTypeTermForType(resultType)
- val defaultValue = primitiveDefaultValue(resultType)
+ def assign(action: GeneratedExpression): String =
+ s"""
+ |${action.code}
+ |$nullTerm = ${action.nullTerm};
+ |if (!$nullTerm) {
+ | $resultTerm = ${action.resultTerm};
+ |}
+ |""".stripMargin
- val operatorCode =
- s"""
- |${condition.code}
- |$resultTypeTerm $resultTerm = $defaultValue;
- |boolean $nullTerm;
- |if (${condition.resultTerm}) {
- | ${trueAction.code}
- | $nullTerm = ${trueAction.nullTerm};
- | if (!$nullTerm) {
- | $resultTerm = ${trueAction.resultTerm};
- | }
- |}
- |else {
- | ${falseAction.code}
- | $nullTerm = ${falseAction.nullTerm};
- | if (!$nullTerm) {
- | $resultTerm = ${falseAction.resultTerm};
- | }
- |}
- |""".stripMargin.trim
+ // a null condition is false via its default value
+ val whens = (0 until operands.size - 1 by 2).map {
+ j =>
+ requireBoolean(operands(j))
+ (operands(j), generateCast(ctx, operands(j + 1), resultType,
nullOnFailure = true))
+ }
+ val elseAction = generateCast(ctx, operands.last, resultType,
nullOnFailure = true)
- GeneratedExpression(resultTerm, nullTerm, operatorCode, resultType)
+ // flat guarded blocks instead of nested else keep the splitter output flat
+ val doneTerm = newName(ctx, "done")
+ val branches = whens.zipWithIndex.map {
+ case ((condition, trueAction), i) =>
+ val branch =
+ s"""
+ |${condition.code}
+ |if (${condition.resultTerm}) {
+ | ${assign(trueAction)}
+ | $doneTerm = true;
+ |}
+ |""".stripMargin
+ // the first branch of a chunk is guarded by its chunk
+ if (i % CASE_CHUNK_WHENS == 0) branch else s"if (!$doneTerm)
{\n$branch\n}"
}
+ // one guard per chunk, so after a match the remaining chunks cost one
check each even when
+ // the code splitter moves their branches into methods
+ val chunks = branches.grouped(CASE_CHUNK_WHENS).zipWithIndex.map {
+ case (chunk, 0) => chunk.mkString("\n")
+ case (chunk, _) => s"if (!$doneTerm) {\n${chunk.mkString("\n")}\n}"
+ }
+ val code =
+ s"""
+ |$resultTypeTerm $resultTerm = $defaultValue;
+ |boolean $nullTerm = true;
+ |boolean $doneTerm = false;
+ |${chunks.mkString("\n")}
+ |if (!$doneTerm) {
+ | ${assign(elseAction)}
+ |}
+ |""".stripMargin.trim
+ GeneratedExpression(resultTerm, nullTerm, code, resultType)
}
+ // Number of WHENs of a CASE behind one shared guard.
+ private val CASE_CHUNK_WHENS = 10
Review Comment:
changed to computed (logic described in comment), however ideally it should
be based on branch code size info which is unavailable here (to help code
splitter)
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