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https://issues.apache.org/jira/browse/CALCITE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17198115#comment-17198115
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Julian Hyde commented on CALCITE-4223:
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bq. Users can implement ColStatistics and add new methods. Then use unwarp() to
get the customized ColStatistics.
That doesn't work, because your {{ColStatistics}} doesn't have an {{unwrap}}
method.
bq. I think ... is much more straightforward and readable.
I don't think readability is the most important metric. The problem is to plug
together providers, which is hard. A robust solution is bound to be somewhat
complex.
bq. Besides, does it mean that RelOptTable has to implement interfaces like
BuiltinMetadata.size/BuiltinMetadata.DistinctRowCount in your proposal?
No. When I call unwrap on an object, it doesn't have to return itself.
Typically it will return a lambda.
> 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: 10m
> 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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