Re: pg_rewind: Skip log directory for file type check like pg_wal

On Mon, 6 Mar 2023 at 19:37, Soumyadeep Chakraborty <
soumyadeep2007(at)gmail(dot)com> wrote:

>
> > 2. Unlike "pg_wal", the "log" directory is not necessarily located
> inside PGDATA. The actual value is configured using "log_directory" GUC,
> which just happened to be "log" by default. And in fact actual values on
> source and target could be different.
>
> I think we only care about files/dirs inside the datadir. Anything
> outside is out of scope for
> pg_rewind AFAIU. We can only address the common case here. As mentioned in
> this
> comment:
>
> * XXX: There is no backend function to get a symbolic link's target in
> * general, so if the admin has put any custom symbolic links in the data
> * directory, they won't be copied correctly.
>

That's exactly my point. Users are very creative.
On one node they could set log_directory to for example "pg_log" and on
another one "my_log".
And they would be writing logs to $PGDATA/pg_log and $PGDATA/my_log
respectively and they are both located inside datadir.

Lets assume that on the source we have "pg_log" and on the target we have
"my_log" (they are configured using "log_directory" GUC).
When doing rewind in this case we want neither to remove the content of
"my_log" on the target nor to copy content of "pg_log" from the source.
It couldn't be achieved just by introducing a static string "log". The
"log_directory" GUC must be examined on both, source and target.

Regards,
--
Alexander Kukushkin