Re: [Patch] Make pg_checksums skip foreign tablespace directories

On Thu, Feb 20, 2020 at 05:38:15PM +0100, Bernd Helmle wrote:
> So i propose a different approach like the attached patch tries to
> implement: instead of just blindly iterating over directory contents
> and filter them out, reference the tablespace location and
> TABLESPACE_VERSION_DIRECTORY directly. This is done by a new function
> scan_tablespaces() which is specialized in just follow the
> symlinks/junctions in pg_tblspc and call scan_directory() with just
> what it has found there. It will also honour directories, just in case
> an experienced DBA has copied over the tablespace into pg_tblspc
> directly.

+       if (S_ISREG(st.st_mode))
+       {
+           pg_log_debug("ignoring file %s in pg_tblspc", de->d_name);
+           continue;
+       }
We don't do that for the normal directory scan path, so it does not
strike me as a good idea on consistency ground.  As a whole, I don't
see much point in having a separate routine which is just roughly a
duplicate of scan_directory(), and I think that we had better just add
the check looking for matches with TABLESPACE_VERSION_DIRECTORY
directly when having a directory, if subdir is "pg_tblspc".  That
also makes the patch much shorter.

+     * the direct path to it and check via lstat wether it exists.
s/wether/whether/, repeated three times.

We should have some TAP tests for that.  The first patch of this
thread from Michael had some, but I would just have added a dummy
tablespace with an empty file in 002_actions.pl, triggering an error
if pg_checksums is not fixed.  Dummy entries around the place where
dummy temp files are added would be fine.
--
Michael