Re: pg_basebackup vs. Windows and tablespaces

On Thu, Nov 13, 2014 at 10:37 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Fri, Nov 14, 2014 at 3:03 AM, Peter Eisentraut <peter_e(at)gmx(dot)net> wrote:
>>
>> On 11/13/14 11:52 AM, Alvaro Herrera wrote:
>> > Amit Kapila wrote:
>> >
>> >> This patch is in "Ready for committer" stage for more than 1.5 months.
>> >> I believe this is an important functionality such that without this tar
>> >> format of pg_basebackup is not usable on Windows. I feel this
>> >> will add a value to pg_basebackup utility and moreover the need
>> >> and design has been agreed upon the list before development.
>> >>
>> >> Can any Committer please have a look at this patch?
>> >
>> > Is this still relevant after this commit?
>> >
>> > commit fb05f3ce83d225dd0f39f8860ce04082753e9e98
>> > Author: Peter Eisentraut <peter_e(at)gmx(dot)net>
>> > Date: Sat Feb 22 13:38:06 2014 -0500
>> >
>> > pg_basebackup: Add support for relocating tablespaces
>>
>> I believe so.
>>
>> The commit only applies to "plain" output. Amit's complaint is that tar
>> utilities on Windows don't unpack symlinks, so the "tar" format isn't
>> useful on Windows when tablespaces are used. So he wants the recovery
>> mechanism to restore the symlinks.
>>
>> I'm not fully on board with that premise. (Get a better tar tool.
>> Submit a patch.)
>>
>
> For native Windows environment, I have checked all the tools I could find
> (Winrar, tar, 7-zip, etc...) and none of them is working and even checked
> a lot on google to try to find some workaround for this, but it seems there
> is no way to reliably handle this issue. Refer link :
> http://sourceforge.net/p/mingw/bugs/2002/
>
> Then I started discussion in tar community to see if they can suggest
> some way, but there also I could not find a reliable solution except that
> it might work in some cases if cygwin is installed. You can refer below
> thread:
> https://lists.gnu.org/archive/html/bug-tar/2014-07/msg00007.html
>
> After spending good amount of time for finding a workaround or alternative,
> only I decided that it is important to write this patch to make tar format
> for pg_basebackup usable for Windows users.
>
>> But this also ties in with the recent discovery that the tar format
>> cannot handle symlinks longer than 99 bytes. So this patch could also
>> fix that problem by putting the untruncated name of the symlink in the
>> WAL data.
>>
>
> I have mentioned that this can be usable for Linux users as well on that
> thread, however I think we might want to provide it with an option for
> linux users. In general, I think it is good to have this patch for Windows
> users and later if we find that Linux users can also get the benefit with
> this functionality, we can expose the same with an additional option.

Why make it an option instead of just always doing it this way?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company