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https://issues.apache.org/jira/browse/VFS-698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16865112#comment-16865112
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David Septimus commented on VFS-698:
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This issue is cause by a call to {{getType()}} inside from {{SftpFileObject}}'s
implementation of {{FileObject.refresh()}}. This forces a {{stat}} call to the
SFTP server to refresh the instance's {{FileType}}.
Based on my understanding of the refresh process, the primary purpose of
{{refresh()}} is to clear the internal state of the {{FileObject}} instance, so
the next operation called on the instance is forced to refresh its state from
the underlying file sytstem. {{SftpFileObject.refresh()}} is the only
implementation that actually makes a file system call.
> SFTP file attributes are fetched multiple times leading to very slow
> directory listing
> --------------------------------------------------------------------------------------
>
> Key: VFS-698
> URL: https://issues.apache.org/jira/browse/VFS-698
> Project: Commons VFS
> Issue Type: Bug
> Affects Versions: 2.3
> Reporter: krishnan
> Priority: Major
>
> getChildren() applied on SftpFileObject is very slow compared to JSCH
> implementation. This is because, the SftpATTRS which is readily available for
> the children after an "ls" call is again fetched for each child file since
> they are independently resolved. So if a directory contains 10 files, it
> results in 1 (ls) + 10 (stat) calls to server.
> For a folder with 100 files (AWS), it took about 35 secs instead of 1.5 secs
> to getChildren().
>
> *doListChildrenResolved:*
> {{final FileObject fo =
> getFileSystem().resolveFile(getFileSystem().getFileSystemManager()}}
> \{{ .resolveName(getName(), UriParser.encode(name), NameScope.CHILD));}}
> {{{color:#ff0000}((SftpFileObject)
> FileObjectUtils.getAbstractFileObject(fo)).setStat(stat.getAttrs());{color}}}
>
> The resolveFile call, creates a SftpFileObject and calls its resolve method,
> which results in getting the (stats) SftpATTRS for each child file. This stat
> is already available as part of the 'ls' call we made. The setStat call above
> (highlighted is red) is redundant, since stat for each child file is already
> fetched one at a time.
> The solution would be to avoid getting the stat for each child file after an
> 'ls' call. May be, the framework makes it difficult to do this easily.
>
>
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