Horton

Re: pg11+: pg_ls_*dir LIMIT 1: temporary files .. not closed at end-of-transaction

Tom Lane <tgl@sss.pgh.pa.us>

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: pgsql-hackers@postgresql.org, Fabien COELHO <coelho@cri.ensmp.fr>, Alvaro Herrera <alvherre@2ndquadrant.com>, David Steele <david@pgmasters.net>, "Bossart, Nathan" <bossartn@amazon.com>, Thomas Munro <thomas.munro@gmail.com>
Date: 2020-03-29T17:22:04Z
Lists: pgsql-hackers 
Justin Pryzby <pryzby@telsasoft.com> writes:
> On Sun, Mar 29, 2020 at 12:37:05PM -0400, Tom Lane wrote:
>> After looking at the callers of pg_ls_dir_files, and noticing that
>> it's already defined to ignore anything that's not a regular file,
>> I think switching to lstat makes sense.

> Yea, only pg_ls_dir() shows special file types (and currently the others even
> hide dirs).

> The essence of your patch is to ignore ENOENT, but you also changed to use
> lstat(), which seems unrelated.  That means we'll now hide (non-broken)
> symlinks.  Is that intentional/needed ?

Well, the following comment says "ignore anything but regular files",
so I'm supposing that that is the behavior that we actually want here
and failed to implement correctly.  There might be scope for
additional directory-reading functions, but I'd think you'd want
more information (such as the file type) returned from anything
that doesn't act this way.

In practice, since these directories shouldn't contain symlinks,
it's likely moot.  The only place in PG data directories where
we actually expect symlinks is pg_tablespace ... and that contains
symlinks to directories, so that this function would ignore them
anyway.

			regards, tom lane

Commits

  1. Teach pg_ls_dir_files() to ignore ENOENT failures from stat().

  2. Remove useless pfree()s at the ends of various ValuePerCall SRFs.

  3. Avoid holding a directory FD open across assorted SRF calls.

  4. Document pg_ls_*dir hiding of directories and special files

  5. Avoid holding a directory FD open across pg_ls_dir_files() calls.

  6. Adjust nodeFunctionscan.c to reset transient memory context between calls