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

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16241396#comment-16241396 ] 

Julian Hyde commented on CALCITE-2035:
--------------------------------------

[~gian], [~bslim], [~jcamachorodriguez], Can one of your please review my proposed fix in https://github.com/julianhyde/calcite/commits/2035-approx-count-distinct.

> 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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