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https://issues.apache.org/jira/browse/DRILL-8290?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17598995#comment-17598995
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ASF GitHub Bot commented on DRILL-8290:
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jnturton commented on PR #2636:
URL: https://github.com/apache/drill/pull/2636#issuecomment-1234361083
@vvysotskyi I did spot one [other recursive file
listing](https://github.com/jnturton/drill/blob/65fb7ddc144ecae5330c9325af63010748f74cdf/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/metadata/Metadata.java#L376)
that could possibly use the short cut in this PR if I propagate a `limit0`
flag down to it.
It appears to be invoked only if there are Parquet files present at the top
level of the queried path which I don't think should be too common for big
datasets since data files are generally only present at the leaves of the
directory tree. So I thought I'd ask if you think it's worth trying to
implement the single file short cut here too, or we just leave it alone?
> Short cut recursive file listings for LIMIT 0 queries
> -----------------------------------------------------
>
> Key: DRILL-8290
> URL: https://issues.apache.org/jira/browse/DRILL-8290
> Project: Apache Drill
> Issue Type: Improvement
> Components: Query Planning & Optimization
> Affects Versions: 1.20.2
> Reporter: James Turton
> Priority: Minor
> Fix For: 2.0.0
>
>
> The existing LIMIT 0 query optimisations do not prevent a query run against
> the top of a deep DFS directory tree from recursively listing FileStatuses
> for everything within it using a pool of worker threads. This Issue proposes
> a new optimisation whereby such queries will recurse into the directory tree
> on a single thread that returns as soon as any single FileStatus has been
> obtained.
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