gengliangwang commented on code in PR #56971:
URL: https://github.com/apache/spark/pull/56971#discussion_r3530515207
##########
sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/NullExpressionsSuite.scala:
##########
@@ -20,6 +20,7 @@ package org.apache.spark.sql.catalyst.expressions
import java.sql.Timestamp
import org.apache.spark.{SparkFunSuite, SparkRuntimeException}
+import org.apache.spark.sql.catalyst.InternalRow
Review Comment:
Fixed — reordered so `FunctionIdentifier` precedes `InternalRow`.
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullExpressions.scala:
##########
@@ -93,11 +93,37 @@ case class Coalesce(children: Seq[Expression])
}
override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ // Fast path for the common `coalesce(a, b)` where `b` is non-nullable and
its evaluation
+ // generates no code (a literal or an already-evaluated value), e.g. the
`coalesce(sum, 0)`
+ // emitted for every SUM/AVG update. The result can never be null and `b`
carries a pure
+ // Java expression, so a single ternary replaces the general do-while
block below and no
+ // global mutable isNull state is needed. The empty-code requirement also
preserves lazy
+ // evaluation: there are no statements of `b` to hoist before the null
check.
+ val probedEvals: Option[Seq[ExprCode]] =
+ if (children.length == 2 && !children(1).nullable) {
+ val first = children(0).genCode(ctx)
+ val second = children(1).genCode(ctx)
+ if (second.code.isEmpty) {
+ val resultType = CodeGenerator.javaType(dataType)
Review Comment:
Good catch — hoisted `val resultType = CodeGenerator.javaType(dataType)` to
the top of `doGenCode` so it's computed once and shared by both the fast path
and the general path.
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullExpressions.scala:
##########
@@ -93,11 +93,37 @@ case class Coalesce(children: Seq[Expression])
}
override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ // Fast path for the common `coalesce(a, b)` where `b` is non-nullable and
its evaluation
+ // generates no code (a literal or an already-evaluated value), e.g. the
`coalesce(sum, 0)`
+ // emitted for every SUM/AVG update. The result can never be null and `b`
carries a pure
+ // Java expression, so a single ternary replaces the general do-while
block below and no
+ // global mutable isNull state is needed. The empty-code requirement also
preserves lazy
+ // evaluation: there are no statements of `b` to hoist before the null
check.
+ val probedEvals: Option[Seq[ExprCode]] =
+ if (children.length == 2 && !children(1).nullable) {
+ val first = children(0).genCode(ctx)
Review Comment:
Done — switched to `children.head`.
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