liyafan82 commented on a change in pull request #1907: [CALCITE-3909]
RelMdMinRowCount doesn't take into account UNION DISTINCT
URL: https://github.com/apache/calcite/pull/1907#discussion_r407300852
##########
File path:
core/src/main/java/org/apache/calcite/rel/metadata/RelMdMinRowCount.java
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@@ -61,7 +61,12 @@ public Double getMinRowCount(Union rel, RelMetadataQuery
mq) {
rowCount += partialRowCount;
}
}
- return rowCount;
+
+ if (rel.all) {
+ return rowCount;
+ } else {
+ return Math.min(rowCount, 1d);
+ }
Review comment:
Maybe there is a potential improvement here: if rel.all == false, and once
we find the current value of rowCount greater than 1d, we can stop the loop
early and directly return 1d.
It also makes the code less readable, so I am not sure if it is worth it.
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