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Re: Table rewrites vs. pending AFTER triggers

From: Martijn van Oosterhout <kleptog(at)svana(dot)org>
To: Gokulakannan Somasundaram <gokul007(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <adunstan(at)postgresql(dot)org>,Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Table rewrites vs. pending AFTER triggers
Date: 2008-01-03 10:23:31
Message-ID: 20080103102331.GA30497@svana.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Jan 03, 2008 at 01:08:47PM +0530, Gokulakannan Somasundaram wrote:
> Can you please explain, any specific use-case where DDLs are necessary
> within a transaction?

I don't think they are ever necessary, they're just very very nice. For
example:

- You want a new column to appear populated  on a table atomically. You
do a BEGIN; add column; update set column=foo; add foreign key; COMMIT
- Installation of external modules can be done atomically, so you don't
end up with half installed contrib modules.
- Principle of Least Surprise. Automatic commit for any reason seems
wrong.
- Temporarily disabling triggers/indexes/constraints, if the system
aborts/crashes, the triggers are reinstated automatically.
- Just general niceity of being able to test schema changes without
immediatly changing the system.

There are many more...

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog(at)svana(dot)org>   http://svana.org/kleptog/
> Those who make peaceful revolution impossible will make violent revolution inevitable.
>  -- John F Kennedy

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Subject: Re: Table rewrites vs. pending AFTER triggers
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