Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/21886#discussion_r205575498
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -1407,6 +1408,87 @@ object ReplaceExceptWithAntiJoin extends
Rule[LogicalPlan] {
}
}
+/**
+ * Replaces logical [[Intersect]] operator using a combination of Union,
Aggregate
+ * and Generate operator.
+ *
+ * Input Query :
+ * {{{
+ * SELECT c1 FROM ut1 INTERSECT ALL SELECT c1 FROM ut2
+ * }}}
+ *
+ * Rewritten Query:
+ * {{{
+ * SELECT c1
+ * FROM (
+ * SELECT replicate_row(min_count, c1) AS (min_count, c1)
+ * FROM (
+ * SELECT c1,
+ * vcol1_cnt,
+ * vcol2_cnt,
+ * IF (vcol1_cnt > vcol1_cnt, vcol2_cnt, vcol1_cnt) AS
min_count
+ * FROM (
+ * SELECT c1, count(vcol1) as vcol1_cnt, count(vcol2)
as vcol2_cnt
+ * FROM (
+ * SELECT c1, true as vcol1, null as vcol2 FROM ut1
+ * UNION ALL
+ * SELECT c1, null as vcol1, true as vcol2 FROM ut2
--- End diff --
Based on the implementation, I think this should be:
```
SELECT true as vcol1, null as vcol2, c1 FROM ut1
UNION ALL
SELECT null as vcol1, true as vcol2, c1 FROM ut2
```
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