Re: Adding WHERE clause to pg_dump - Mailing list pgsql-hackers

On Fri, 2008-07-25 at 14:11 -0700, daveg wrote:
> On Fri, Jul 25, 2008 at 08:26:35PM +0100, Simon Riggs wrote:
> > 
> > On Fri, 2008-07-25 at 11:46 -0700, Joshua D. Drake wrote:
> > > On Fri, 2008-07-25 at 19:33 +0100, Simon Riggs wrote:
> > > > On Fri, 2008-07-25 at 13:31 -0400, Tom Lane wrote:
> > > > > Simon Riggs <simon@2ndquadrant.com> writes:
> > > > > > Attached patch implements WHERE clauses for pg_dump.
> > > > > 
> > > > > I still have serious reservations about adding such an ugly,
> > > > > non-orthogonal wart to pg_dump.  Why is it not appropriate to just
> > > > > do a COPY (SELECT ...) TO STDOUT when you need this?
> > > > 
> > > > So you can dump a coherent sample database in one command, not 207.
> > > > 
> > > > Every user of PostgreSQL wants a dev/test database. If the database is
> > > > large it isn't practical to take a complete copy. Nor is it practical to
> > > > hand-write a data sampling extraction program and if you do, its usually
> > > > imperfect in many ways.
> > > > 
> > > > Adding this feature gives a very fast capability to create sample
> > > > databases, or incremental backups for many cases.
> > > 
> > > Not sure I buy this argument. I am all for usability and I would be the
> > > first to shout about the general ridiculousness of pg_dump/all/restore
> > > but in this case I think Tom is right. This feature could easily be done
> > > in a script without harassing pg_dump.
> > 
> > You can do it, yes. But it takes a lot longer. If the time to implement
> > was similar, then I would immediately agree "feature available already".
> > 
> > pg_dump is not "harassed" by this. What is lost by adding this feature?
> 
> This was discussed at the beginning of June on patches, Dave Durham submitted
> a patch to add where clauses via a -w option and then in response to feedback
> to add it to each each table of -t. See discussion here:
> 
>   http://archives.postgresql.org/pgsql-patches/2008-06/msg00001.php
> 
> and final patch here:
> 
>   http://archives.postgresql.org/pgsql-patches/2008-06/msg00026.php.
> 
> We now have two patches on this topic from different submitters with
> different use cases supplied as justification. 

Well, that is truly bizarre.

I had no idea about the existence of the other patch. I guess I must
have been busy that week.

This was designed a while back in conjunction with other related
thoughts. I still want an easy way to create a data sample for creating
dev databases from large production systems.

I defer and apologise to the previous submitter, since he got there
first, and apologise again for the noise.

(Cheeky code review: Davy's patch fails if used with -o option, plus I
think it outputs the wrong text into the dump file, AFAICS).

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support