Julian Hyde created CALCITE-1172:
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Summary: Add rule to flatten two Aggregate operators into one
Key: CALCITE-1172
URL: https://issues.apache.org/jira/browse/CALCITE-1172
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
Assignee: Julian Hyde
If there is an Aggregate on top of an Aggregate, and the top aggregate's group
key is a subset of the lower aggregate's group key, and the aggregates are
expansions of rollups, then a rule would convert into a single aggregate.
For example, SUM of SUM becomes SUM; SUM of COUNT becomes COUNT; MAX of MAX
becomes MAX; MIN of MIN becomes MIN. AVG of AVG would not match, nor would
COUNT of COUNT.
The rule would convert
{noformat}
Aggregate({x}, SUM(c1), MIN(c2), MAX(c3))
Aggregate({x, y}, SUM(c1), MIN(c2), MAX(c3))
R
{noformat}
into
{noformat}
Aggregate({x}, SUM(c1), MIN(c2), MAX(c3))
R
{noformat}
The rule would not work if there was anything between the two {{Aggregate}}
operators.
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