NobiGo commented on code in PR #4459:
URL: https://github.com/apache/calcite/pull/4459#discussion_r2191404200
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core/src/main/java/org/apache/calcite/rel/metadata/RelMdDistinctRowCount.java:
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@@ -172,12 +172,18 @@ protected RelMdDistinctRowCount() {}
return 1D;
}
}
+ // the result of the aggregation function is difficult to infer, so if the
groupKey contains
+ // the aggregated column, return the full row count of Aggregate. This is
the most conservative
+ // estimate, and the actual ndv will not be greater than it.
+ if (groupKey.anyMatch(key -> key >= rel.getGroupCount())) {
Review Comment:
I didn't understand the changes here, but the test cases are good for me.
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