[wp-trac] [WordPress Trac] #50587: Provide short-circuit filter for scandir() in wp_unique_filename()

[WordPress Trac]

#50587: Provide short-circuit filter for scandir() in wp_unique_filename()
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 Reporter:  joehoyle     |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Upload       |    Version:  5.3
 Severity:  normal       |   Keywords:
  Focuses:               |
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 In https://core.trac.wordpress.org/ticket/42437, WordPress introduced an
 enhancement to how unique filenames are calculated. The tl;dr of that
 change was to run `scandir()` on the directory that a file will be placed
 in, and iterate over all files, to check if there is any files that can
 potentially conflict with the newly added file (or future resize
 variants).

 In situations where you have many thousands of files in your monthly
 uploads directories, or where the upload DIR path is particularly slow for
 access (such as remote file systems) this `scandir()` can cause a large
 performance overhead.

 I propose we add a "pre filter" to `scandir()` to allow plugins to
 override the file fetching behaviour. The current implementation is quite
 wasteful, as it will do a list on the whole directory, but then call
 `preg_match()` on each file with `^$filename*...`. In situations where
 plugins can get file listings by other mechanisms, a file list for
 `$dir/$filename*` would return many fewer results but provide the same
 file list needed for `_wp_check_existing_file_names()` for example.

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Ticket URL: <https://core.trac.wordpress.org/ticket/50587>
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