c21 commented on a change in pull request #31318:
URL: https://github.com/apache/spark/pull/31318#discussion_r585308290
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
##########
@@ -157,6 +157,28 @@ trait PredicateHelper extends AliasHelper with Logging {
}
}
+ /**
+ * Builds a balanced output predicate in bottom up approach, by applying
binary operator op
+ * pair by pair on input predicates exprs recursively.
+ * Example: exprs = [a, b, c, d], op = And, returns (a And b) And (c And d)
+ * exprs = [a, b, c, d, e, f], op = And, returns ((a And b) And (c And d))
And (e And f)
+ */
+ protected def buildBalancedPredicate[Expression](
+ exprs: Seq[Expression], op: (Expression, Expression) => Expression):
Expression = {
+ exprs match {
+ case Seq(expression) => expression
+ case expressions =>
+ val grouped = expressions.grouped(2).toSeq
+ val pairwiseExprs = for (g <- grouped) yield {
+ g match {
+ case Seq(a, b) => op(a, b)
+ case Seq(x) => x
+ }
+ }
+ buildBalancedPredicate(pairwiseExprs, op)
Review comment:
nit: shall we write in a more scala way?
e.g.
```
case expressions =>
val pairwiseExprs = expressions.grouped(2).map {
case Seq(e1, e2) => op(e1, e2)
case Seq(e) => e
}
buildBalancedPredicate(pairwiseExprs.toSeq, op)
```
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