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https://issues.apache.org/jira/browse/CALCITE-4215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191032#comment-17191032
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Vladimir Sitnikov commented on CALCITE-4215:
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One of the issues is {{double
org.apache.calcite.rel.RelNode#estimateRowCount(RelMetadataQuery mq)}}.
In other words the method must return non-nullable double, however it is often
implemented as {{mq.getRowCount(...)}}.
If metadata can return nullable rowCount, then it must be converted to
non-nullable {{double}} somehow.
So either we deprecate {{double estimateRowCount}} method and create {{Double
estimateRowCount}}, or we go with {{getRowCount}} / {{getRowCountOrNull}} in
the metadata class.
> Ensure org.apache.calcite.schema.Statistic uses null vs emptyList
> appropriately
> -------------------------------------------------------------------------------
>
> Key: CALCITE-4215
> URL: https://issues.apache.org/jira/browse/CALCITE-4215
> Project: Calcite
> Issue Type: Sub-task
> Components: core
> Affects Versions: 1.25.0
> Reporter: Vladimir Sitnikov
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> null: statistic is *not* *known*
> emptyList: statistic is *known*, and the value is *empty* (e.g. no unique
> keys in the table)
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