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https://issues.apache.org/jira/browse/CALCITE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17190493#comment-17190493
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Chunwei Lei commented on CALCITE-4223:
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[~amaliujia] , column stats are used in Hive[1], Flink[2], Spark[3].
[1]
[https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/plan/ColStatistics.java]
[2][https://github.com/apache/flink/blob/master/flink-table/flink-table-common/src/main/java/org/apache/flink/table/plan/stats/ColumnStats.java]
[[3]
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/columnar/ColumnStats.scala|https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/columnar/ColumnStats.scala]
> 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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