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https://issues.apache.org/jira/browse/CALCITE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17190362#comment-17190362
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Julian Hyde commented on CALCITE-4223:
--------------------------------------
Do they really need to be part of {{interface RelOptTable}}? I added
{{interface Statistic}} and the {{Table.getStatistic()}} method to make it easy
for people to write user-defined tables. But the intention was only ever to
deal with simple statistics.
For more complex statistics, use {{RelMetadataQuery}}, and add your own
metadata provider.
We already have {{RelMdPopulationSize}}, which gives cardinality for single
columns and groups of columns. What other stats do you have in mind?
> 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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