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Date: Sat, 21 Dec 2024 11:10:12 +0100
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Subject: Re: [PHP-DEV] Discussion: Remove file statcache?
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To: Larry Garfield <larry@garfieldtech.com>,
 php internals <internals@lists.php.net>
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From: cmbecker69@gmx.de ("Christoph M. Becker")

On 21.12.2024 at 06:49, Larry Garfield wrote:

> On Fri, Dec 20, 2024, at 3:35 PM, Christoph M. Becker wrote:
>
>> I still think the stat cache should be *deprecated* first.  That gives
>> users a chance to reconsider calling multiple stat related functions
>> instead of doing a single stat() call.  See my previous comment[1] for
>> some further details.
>>
>> [1] <https://github.com/php/php-src/pull/5894#issuecomment-2546473892>
>
> What exactly would deprecation look like here?  My plan was to just rip =
the cache out, and update clearstatcache() to be a no-op, but issue a depr=
ecation message "Hey, this doesn't do anything anymore."  And then we can =
remove the function itself in like PHP 10 or something, because it doesn't=
 hurt anything to leave it be.
>
> I don't see there being much value to a period of "hey, this is *going* =
to do nothing in the future", when users couldn't do anything about it.  T=
hat just gives them a deprecation notice they cannot fix, if they're in on=
e of the very few situations where manually clearing the cache is useful. =
 That doesn't seem great.

I believe the whole point of the stat cache is to optimize multiple
consecutive calls to stat releted functions on the same file *name*.
E.g. code like

  $mtime =3D filemtime($filename);
  $fsize =3D filesize($filename);

would be a relevant example.  Such code could be changed in userland to

  $stat =3D stat($filename);
  $mtime =3D $stat["mtime"];
  $fsize =3D $stat["stat"];

where the stat cache would be irrelevant.  Of course, users who are not
aware that there may be a difference in performance won't even think
about that.  As such a deprecation message could be triggered whenever
the stat cache is hit, possibly pointing also to the file:line where the
cache had been populated.  The usefulness of this is based on the
assumption that it's pretty unlikely that the stat cache is hit from
unrelated code paths.

If a general deprecation is not desired (and that seems to be the case),
I'm also fine with a PR/patch that users could apply themselves, similar
what Nikita did back then when string to number comparisons changed[1].

Note that clearstatcache() should not be no-opped altogether; clearing
(parts of) the realpath cache seems still useful.

[1] <https://github.com/php/php-src/pull/3917>

Christoph