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Re: pg_dump --split patch

From: Joel Jacobson <joel(at)gluefinance(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: pg_dump --split patch
Date: 2010-12-28 16:41:04
Message-ID: AANLkTi=a=DpBMhc=Ab_ubM8vq5QrSP02TrSfWPqwEm1m@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2010/12/28 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>

> Joel Jacobson <joel(at)gluefinance(dot)com> writes:
> > Dear fellow hackers,
> > Problem: A normal diff of two slightly different schema dump files
> (pg_dump
> > -s), will not produce a user-friendly diff, as you get all changes in the
> > same file.
>
> > Solution: I propose a new option to pg_dump, --split, which dumps each
> > object to a separate file in a user friendly directory structure:
>
> Um ... how does that solve the claimed problem exactly?
>

Because then you can do,
$ diff -r <old schema dump dir> <new schema dump dir>,
instead of,
$ diff <old entire schema dump> <new entire schema dump>
which will nicely reveal each individual object modified, as opposed to a
huge global diff of everything


>
> > [-f filename] : main dump file, imports each splitted part using \i
> > [-f filename]-split/[desc]/[tag]/[oid].sql : dump of the oid
>
> This particular choice seems remarkably *un* friendly, since two dumps
> from different DBs will inevitably not share the same OIDs, making it
> practically impossible to compare them even if they are logically
> identical.  But even without the choice to use OIDs in the filenames
> I'm unconvinced that file-per-object is a good idea in any way shape or
> form.
>

Good point!

To compare two different database, perhaps it's possible to use a sequence,
1,2,...,n for each file in each directory, i.e., /[desc]/[tag]/[n], and to
sort them by something distinct which will ensure the same numbering between
different databases, such as the arguments for functions, or other
properties for other kind of objects. Any ideas?

(In my case, I didn't need to compare schemas between different database. I
needed to compare two dumps created at different points in time of the same
database, which do share the same oids for objects existing in both
versions.)




>
>                        regards, tom lane
>



-- 
Best regards,

Joel Jacobson
Glue Finance

E: jj(at)gluefinance(dot)com
T: +46 70 360 38 01

Postal address:
Glue Finance AB
Box  549
114 11  Stockholm
Sweden

Visiting address:
Glue Finance AB
Birger Jarlsgatan 14
114 34 Stockholm
Sweden

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