Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/12850#discussion_r65464426
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -738,6 +739,49 @@ object InferFiltersFromConstraints extends
Rule[LogicalPlan] with PredicateHelpe
}
/**
+ * Reorder associative integral-type operators and fold all constants into
one.
+ */
+object ReorderAssociativeOperator extends Rule[LogicalPlan] {
+ private def isAssociativelyFoldable(e: Expression): Boolean =
+ e.deterministic && e.isInstanceOf[BinaryArithmetic] &&
e.dataType.isInstanceOf[IntegralType] &&
+ isSingleOperatorExpr(e)
+
+ private def isSingleOperatorExpr(e: Expression): Boolean = e.find {
+ case a: Add if a.getClass == e.getClass => false
+ case m: Multiply if m.getClass == e.getClass => false
+ case _: BinaryArithmetic => true
+ case _ => false
+ }.isEmpty
+
+ private def getOperandList(e: Expression): Seq[Expression] = e match {
+ case BinaryArithmetic(a, b) => getOperandList(a) ++ getOperandList(b)
+ case other => other :: Nil
+ }
+
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case q: LogicalPlan => q transformExpressionsDown {
--- End diff --
how about
```
def flattenAdd(e: Expression): Seq[Expression] = e match {
case Add(l, r) => flattenAdd(l) ++ flattenAdd(r)
case other => other
}
...
plan transformAllExpressions {
case a: Add if a.deterministic && a.dataType.isInstanceOf[IntegralType] =>
val (foldables, others) => flattenAdd(a).partition(_.foldable)
if (foldables.size > 1) {
val foldableExpr = foldables.reduce(Add(_, _))
val c = Literal.create(foldableExpr.eval(), a.dataType)
if (others.isEmpty) c else Add(others.reduce(Add(_, _)), c)
} else {
a
}
}
```
We can duplicate some code for `Multiply`, and I think this maybe more
readable than the current version.
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