Re: ALTER SYSTEM SET typos and fix for temporary file name management

On Tue, Jan 21, 2014 at 7:02 PM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Wed, Jan 22, 2014 at 5:29 AM, Alvaro Herrera
> <alvherre@2ndquadrant.com> wrote:
>> I agree with Michael that having pg_basebackup be aware of the ".temp"
>> suffix is ugly; for instance if we were to fix it to ".tmp" in ALTER
>> SYSTEM but forgot to change pg_basebackup, the check would be
>> immediately broken.  But on the other hand I'm not sure why it's such a
>> problem for pg_basebackup that it needs to be checking in the first
>> place -- how about we rip that out?
> Coupled with the addition of a pgsql_tmp prefix to the temp
> configuration file name would work, yes we could remove this check
> part.
>
>> Perhaps the temp file needs to be in pgsql_tmp?  (Do we need to worry
>> about cross-filesystem links if we do?  I mean, do we support mounting
>> pgsql_tmp separately?)
> Using pgsql_tmp looks a bit weird as well, as this prefix is used only
> for temporary files doing database-related operations, and ALTER
> SYSTEM is not one. Doing that this would need a mention in the docs at
> least:
> http://www.postgresql.org/docs/devel/static/storage-file-layout.html
> Thoughts?

I think moving the temp file to a different directory than the
permanent file is a non-starter.  As Alvaro says, that could be on a
different file system, and then attempting to rename() the file into
place would fail.

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