[jira] [Commented] (CALCITE-4511) The distinct row count and population size for constant columns should be 1

["Liya Fan (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17289762#comment-17289762 ] 

Liya Fan commented on CALCITE-4511:
-----------------------------------

[~julianhyde] I have updated the case title and commit message accordingly, and added support for PopulationSize.
Thanks a lot for your kind reminder. I will be careful next time. 

> The distinct row count and population size for constant columns should be 1
> ---------------------------------------------------------------------------
>
>                 Key: CALCITE-4511
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4511
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: Liya Fan
>            Assignee: Liya Fan
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Suppose we have a relation with 3 columns: {{(a, '1', '2')}}. The first column comes from an underlying table, while the other two columns are constants. 
> For this relation, we should have {{NDV(1) = 1}}, since column 1 is a constant, which have only one possible value (suppose the column index starts from 0).
> Similarly, we should have {{NDV(1, 2) = 1}}, since both columns are constants.
> We should also have {{NDV(0, 1) == NDV(0)}}, because the number of distinct values depends on the non-const column, which is {{a}} from the underlying table. 



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