Julian Hyde created CALCITE-1368:
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             Summary: Infer predicates for aggregate functions
                 Key: CALCITE-1368
                 URL: https://issues.apache.org/jira/browse/CALCITE-1368
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde
            Assignee: Julian Hyde


Currently when inferring predicates for Aggregate, Calcite only pulls up 
existing predicates, and it can only do that for columns that are part of the 
group key. This feature would infer predicates based on the behavior of 
aggregate functions and, sometimes, predicates of the arguments to those 
functions.

Examples:
* {{count\(*)}} and {{count\(x)}} are always > 0 (if groups are non-empty, and 
x is not null)
* {{count\(*)}} and {{count\(x)}} are always >= 0
* {{sum\(x)}} is >= 0 (if x is >= 0; it's OK if x is sometimes null)
* {{min\(x)}} and {{max\(x)}} have the same upper and lower bounds as x



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