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https://issues.apache.org/jira/browse/BEAM-4719?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17123272#comment-17123272
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Beam JIRA Bot commented on BEAM-4719:
-------------------------------------
This issue is P2 but has been unassigned without any comment for 60 days so it
has been labeled "stale-P2". If this issue is still affecting you, we care!
Please comment and remove the label. Otherwise, in 14 days the issue will be
moved to P3.
Please see https://beam.apache.org/contribute/jira-priorities/ for a detailed
explanation of what these priorities mean.
> 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: P2
> Labels: stale-P2
>
> 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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