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Re: pg_restore --no-post-data and --post-data-only

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Jim Nasby <jim(at)nasby(dot)net>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_restore --no-post-data and --post-data-only
Date: 2011-08-31 20:03:25
Message-ID: 1314820973-sup-9395@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Excerpts from Jim Nasby's message of mié ago 31 16:45:59 -0300 2011:
> On Aug 26, 2011, at 5:23 PM, Andrew Dunstan wrote:
> > On 08/26/2011 04:46 PM, Jim Nasby wrote:
> >> On Aug 26, 2011, at 12:15 PM, Andrew Dunstan wrote:
> >>> I knew there would be some bike-shedding about how we specify these things, which is why I haven't written docs yet.
> >> While we're debating what shade of yellow to paint the shed...
> >> 
> >> My actual use case is to be able to be able to "inject" SQL into a SQL-formatted dump either pre- or post-data (I'm on 8.3, so I don't actually dump any data; I'm *mostly* emulating the ability to dump data on just certain tables).
> >> 
> >> So for what I'm doing, the ideal interface would be a way to tell pg_dump "When you're done dumping all table structures but before you get to any constraints, please run $COMMAND and inject it's output into the dump output." For some of the data obfuscation we're doing it would be easiest if $COMMAND was a perl script instead of SQL, but we could probably convert it.
> >> 
> >> Of course, many other folks actually need the ability to just spit out specific portions of the dump; I'm hoping we can come up with something that supports both concepts.
> >> 
> > 
> > Well, the Unix approach is to use tools that do one thing well to build up more complex tools. Making pg_dump run some external command to inject things into the stream seems like the wrong thing given this philosophy. Use pg_dump to get the bits you want (pre-data, post-data) and sandwich them around whatever else you want.
> 
> I agree... except for one little niggling concern: If pg_dump is injecting something, then the DDL is being grabbed with a single, consistent snapshot. --pre and --post do not get you that (though we could probably use the new ability to export snapshots to fix that...)

Eh, --pre and --post are pg_restore flags, so you already have a
consistent snapshot.

-- 
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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