viirya commented on a change in pull request #25717: [WIP][SPARK-29013][SQL]
Structurally equivalent subexpression elimination
URL: https://github.com/apache/spark/pull/25717#discussion_r322017093
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala
##########
@@ -65,6 +65,40 @@ case class BoundReference(ordinal: Int, dataType: DataType,
nullable: Boolean)
}
}
+/**
+ * This bound reference points to a parameterized slot in an input tuple. It
is used in
+ * common sub-expression elimination. When some common sub-expressions have
same structural
+ * but different slots of input tuple, we replace `BoundReference` with this
parameterized
+ * version. The slot position is parameterized and is given at runtime.
+ */
+case class ParameterizedBoundReference(parameter: String, dataType: DataType,
nullable: Boolean)
+ extends LeafExpression {
+
+ override def toString: String = s"input[$parameter,
${dataType.simpleString}, $nullable]"
+
+ override def eval(input: InternalRow): Any = {
+ throw new UnsupportedOperationException(
+ "ParameterizedBoundReference does not implement eval")
+ }
+
+ override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ assert(ctx.currentVars == null && ctx.INPUT_ROW != null,
+ "ParameterizedBoundReference can not be used in whole-stage codegen
yet.")
Review comment:
I think it can be used in whole-stage codegen. As this is applied to
sub-expression elimination which is non whole-stage only, I'd also like to
reduce the change of code in a single PR.
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