wangyum commented on a change in pull request #28575:
URL: https://github.com/apache/spark/pull/28575#discussion_r434458943
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -1372,6 +1376,108 @@ object PushPredicateThroughJoin extends
Rule[LogicalPlan] with PredicateHelper {
}
}
+/**
+ * Rewriting join condition to conjunctive normal form expression so that we
can push
+ * more predicate.
+ */
+object PushPredicateThroughJoinByCNF extends Rule[LogicalPlan] with
PredicateHelper {
+ /**
+ * Rewrite pattern:
+ * 1. (a && b) || c --> (a || c) && (b || c)
+ * 2. a || (b && c) --> (a || b) && (a || c)
+ *
+ * To avoid generating too many predicates, we first group the filter
columns from the same table.
+ */
+ private def toCNF(condition: Expression, depth: Int = 0): Expression = {
+ if (depth < SQLConf.get.maxRewritingCNFDepth) {
+ condition match {
+ case or @ Or(left: And, right: And) =>
+ val lhs =
splitConjunctivePredicates(left).groupBy(_.references.map(_.qualifier))
+ val rhs =
splitConjunctivePredicates(right).groupBy(_.references.map(_.qualifier))
+ if (lhs.size > 1) {
+ lhs.values.map(_.reduceLeft(And)).map { c =>
+ toCNF(Or(toCNF(c, depth + 1), toCNF(right, depth + 1)), depth +
1)
Review comment:
This is a special case of **`(a && b) || c`**. E.g.: `(a && b) || (c &&
d)`. The rewriting steps are:
`(a && b) || (c && d)` --> `(a || (c && d)) && (b || (c && d))` --> `(a ||
c) && (a || d) && (b || c) && (b && d)`.
TPC-DS Q13:
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