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https://issues.apache.org/jira/browse/HADOOP-13371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15441330#comment-15441330
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Steve Loughran commented on HADOOP-13371:
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There's a more minimal strategy here which is lower risk and culls some of the
obvious inefficiencies
# when a pattern without regexps come in, revert to a fast list
# If, the pattern is just a trailing `/*.suffix` entry, listFiles -with filter.
Or even better, give the trailing suffix as the terminator for the listing, so
having the blobstore do the filtering.
# if the pattern has a trailing * patterns, list everything in the parent dir.
you could probably combine 2 & 3 to match */*.gz patterns.
trying to handle deeper paths, like */*/* is harder because that's actually
asking for all paths exactly three deep.
We're hampered a bit by the way the API returns a full array, stopping us
querying as the iteration goes along.
Also: need to retain that special 'null' return use case purely because the FS
shell needs it.
> S3A globber to use bulk listObject call over recursive directory scan
> ---------------------------------------------------------------------
>
> Key: HADOOP-13371
> URL: https://issues.apache.org/jira/browse/HADOOP-13371
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs, fs/s3
> Affects Versions: 2.8.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
>
> HADOOP-13208 produces O(1) listing of directory trees in
> {{FileSystem.listStatus}} calls, but doesn't do anything for
> {{FileSystem.globStatus()}}, which uses a completely different codepath, one
> which does a selective recursive scan by pattern matching as it goes down,
> filtering out those patterns which don't match. Cost is
> O(matching-directories) + cost of examining the files.
> It should be possible to do the glob status listing in S3A not through the
> filtered treewalk, but through a list + filter operation. This would be an
> O(files) lookup *before any filtering took place*.
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