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https://issues.apache.org/jira/browse/CALCITE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17202982#comment-17202982
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Danny Chen commented on CALCITE-4223:
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> Maybe they didn't know how

We write our own metadata and check the {{ColumnStatistic}} in it. For common 
metadata extending from Calcite, yes, we have no good way to integrate.

> Introducing column statistics to RelOptTable
> --------------------------------------------
>
>                 Key: CALCITE-4223
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4223
>             Project: Calcite
>          Issue Type: Improvement
>            Reporter: Chunwei Lei
>            Assignee: Chunwei Lei
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> Many systems depend on column statistics to compute more accurate stats, such 
> as NDV, average column size, and so on. It would be nice if Calcite can 
> provide such an interface.
> Column statistics might include NDV, average/max column length, number of 
> nulls, number of trues, number of falses and so on. 
> What do you think?
>  



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