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https://issues.apache.org/jira/browse/HADOOP-13371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15380777#comment-15380777
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Steve Loughran commented on HADOOP-13371:
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Given {{GlobFilter}} is a path filter, a naive implementation could use a
variant of {{listFiles(recursive=true, filter=globFilter)}} —a variant as that
method only lists files, not directories. We'd need a
{{listFilesAndDirectories()}} or similar
This could eliminate the directory calls on deep trees, but be a performance
killer on a wide bucket. The glob scan should be designed to start as far down
the tree as possible.
# Expand the patterns
# Identify the longest list of non-wildcard components in each pattern(s)
# do recursive listings under there if the pattern looks ilke it is designed to
go down at least one child dir. If not, only go down / (reduces size of return
dataset)
# insert results in a sorted tree structure (avoids the sort afterwards)
# On later patterns, see if their paths have already been searched (is this
possible?)
> 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
>
> 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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