[GitHub] [spark] c21 commented on a change in pull request #31318: [SPARK-34222][SQL] Enhance boolean simplification rule

[GitBox <gi...@apache.org>]

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
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@@ -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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