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https://issues.apache.org/jira/browse/FLINK-11822?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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godfrey he updated FLINK-11822:
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Summary: Introduce Flink metadata handlers (was: Introduce Flink metadata
handler)
> Introduce Flink metadata handlers
> ---------------------------------
>
> Key: FLINK-11822
> URL: https://issues.apache.org/jira/browse/FLINK-11822
> Project: Flink
> Issue Type: New Feature
> Components: API / Table SQL
> Reporter: godfrey he
> Assignee: godfrey he
> Priority: Major
>
> Calcite has defined various metadata handlers(e.g. `RowCount`, `Selectivity`)
> and provided default implementation(e.g. `RelMdRowCount`,
> `RelMdSelectivity`). However, the default implementation can't completely
> meet our requirements, e.g. some of its logic is incompleteļ¼and some
> `RelNode`s are not considered.
> There are two options to meet our requirements:
> option 1. Extends from default implementation, overrides method to improve
> its logic, add new methods for new `RelNode`. The advantage of this option is
> we just need to focus on the additions and modifications. However, its
> shortcomings are also obvious: we have no control over the code of
> non-override methods in default implementation classes especially when
> upgrading the Calcite version.
> option 2. Extends from metadata handler interfaces, reimplement all the
> logic. Its shortcomings are very obvious, however we can control all the code
> logic that's what we want.
> so we choose option 2!
> In this jira, only basic metadata handles will be introduce, including:
> `FlinkRelMdPercentageOriginalRow`,
> `FlinkRelMdNonCumulativeCost`,
> `FlinkRelMdCumulativeCost`,
> `FlinkRelMdRowCount`,
> `FlinkRelMdSize`,
> `FlinkRelMdSelectivity`,
> `FlinkRelMdDistinctRowCoun`,
> `FlinkRelMdPopulationSize`,
> `FlinkRelMdColumnUniqueness`,
> `FlinkRelMdUniqueKeys`
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