Steven Talbot created CALCITE-3957:
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Summary: AggregateMergeRule should be able to merge SUM0 into
COUNT even with empty group by
Key: CALCITE-3957
URL: https://issues.apache.org/jira/browse/CALCITE-3957
Project: Calcite
Issue Type: Bug
Reporter: Steven Talbot
Basically, the comment at
[https://github.com/apache/calcite/blame/571731b80a58eb095ebac7123285c375e7afff90/core/src/main/java/org/apache/calcite/rel/rules/AggregateMergeRule.java#L117-L120]
does not apply if the top aggregate is a SUM0, I believe. Without a fix for
this, there's this one case where this rule falls down and isn't able to merge
something that just got rolled up: otherwise it's a pretty nice invariant that
if one of our standard rollup rules for aggregates (say, in
MaterializedViewRule) just split the aggregate, this rule should be able to
merge it back.
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