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https://issues.apache.org/jira/browse/BEAM-4719?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17137716#comment-17137716
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Beam JIRA Bot commented on BEAM-4719:
-------------------------------------
This issue was marked "stale-P2" and has not received a public comment in 14
days. It is now automatically moved to P3. If you are still affected by it, you
can comment and move it back to P2.
> Enhanced LIMIT support
> ----------------------
>
> Key: BEAM-4719
> URL: https://issues.apache.org/jira/browse/BEAM-4719
> Project: Beam
> Issue Type: New Feature
> Components: dsl-sql
> Reporter: Kenneth Knowles
> Priority: P3
>
> Currently, Beam SQL supports LIMIT in two ways:
> 1. Within a query, the results are subject to LIMIT. This works.
> 2. The shell knows to cancel a pipeline when the limit is reached, even if
> there is unfinished unbounded data.
> The canceling of a pipeline works via a basic pattern match against the query
> execution plan, checking a few child nodes of the BeamEnumerableConverter for
> a BeamSortRel without a collation. If it can figure out what the limit is for
> the outermost query, then it will cancel the pipeline.
> A more robust approach might be to use traits (or some other thorough
> analysis) to see if there is a known size for the outermost query. This
> would, for example, be unaffected by any number of layer of non-size-changing
> transformations.
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