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Posted to dev@calcite.apache.org by "Julian Hyde (JIRA)" <ji...@apache.org> on 2017/11/07 01:14:00 UTC

[jira] [Created] (CALCITE-2035) Add APPROX_COUNT_DISTINCT aggregate function

Julian Hyde created CALCITE-2035:
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             Summary: Add APPROX_COUNT_DISTINCT aggregate function
                 Key: CALCITE-2035
                 URL: https://issues.apache.org/jira/browse/CALCITE-2035
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde
            Assignee: Julian Hyde


Add {{APPROX_COUNT_DISTINCT}} aggregate function. The effect of {{APPROX_COUNT_DISTINCT(args)}} is the same as {{COUNT(DISTINCT args)}} but the planner may generate approximate results (e.g. by using HyperLogLog).

Note "may" not "must", above: the planner may choose a plan that returns exact results.

This is a step towards CALCITE-1588, which would allow an {{APPROXIMATE}} clause and specify in more detail the degree of approximation allowed.



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