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Re: bug report: pg_dump does not use CASCADE in DROP

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Preston Landers <planders(at)journyx(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: bug report: pg_dump does not use CASCADE in DROP
Date: 2003-08-30 16:41:26
Message-ID: 200308301641.h7UGfQ412819@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Should we be using CASCADE?  Seems that is going to double-drop some
> > tables.
> 
> It kinda scares me too.  If you are loading into a database that already
> has stuff in it, seems like CASCADE could lead to dropping stuff that is
> not part of the dataset being loaded.
> 
> If you have no stuff in the database that is not part of the dataset
> being loaded, then there's no percentage in individual DROP commands
> anyway --- you'd be better off to drop the whole DB, create a new one,
> and run the restore without any DROPs.  So AFAICS the use of DROP in
> restores is intended for reloading part of an existing database.
> As such, automatic DROP CASCADEs seem like an excellent foot-gun.
> Much safer to do the required drops manually before running restore.
> 
> It might be okay as an option in pg_restore, but not as default
> behavior.

Once pg_dump starts using the dependency information, it seems it could
do the drops in the proper order, and when it detects
mutually-dependent tables, it can use a single DROP CASCADE to remove
them all --- seems like that is a TODO.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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