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https://issues.apache.org/jira/browse/CALCITE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191409#comment-17191409
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Chunwei Lei commented on CALCITE-4223:
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Let me make myself clear. What in my mind is that there is a method called
getColumnStatistics() in RelOptTable. Thus, we can get NDV(or other statistics)
of TableScan easily via
{{rel.getTable().getColumnStatistics().get(columnName).getNdv()}}. The
implementation of it can be delgated to {{Statistic#getColumnStatistics()}}. Do
you have any other ideas?
> 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
>
> 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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