gengliangwang commented on a change in pull request #28805:
URL: https://github.com/apache/spark/pull/28805#discussion_r448143683
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
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@@ -249,8 +251,36 @@ trait PredicateHelper extends Logging {
resultStack.top
}
- private def groupExpressionsByQualifier(expressions: Seq[Expression]):
Seq[Expression] = {
-
expressions.groupBy(_.references.map(_.qualifier)).map(_._2.reduceLeft(And)).toSeq
+ /**
+ * Convert an expression to conjunctive normal form when pushing predicates
through Join,
+ * when expand predicates, we can group by the qualifier avoiding generate
unnecessary
+ * expression to control the length of final result since there are multiple
tables.
+ *
+ * @param condition condition need to be converted
+ * @return the CNF result as sequence of disjunctive expressions. If the
number of expressions
+ * exceeds threshold on converting `Or`, `Seq.empty` is returned.
+ */
+ def conjunctiveNormalFormAndGroupExpsByQualifier(condition: Expression):
Seq[Expression] = {
Review comment:
On second thought, the method name
`conjunctiveNormalFormAndGroupExpsByQualifier` is too long and the `And` is
weird.
How about changing to `CNFWithGroupExpressionsByQualifier`?
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