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Re: DELETE with LIMIT (or my first hack)

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Daniel Loureiro <loureirorg(at)gmail(dot)com>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Csaba Nagy <ncslists(at)googlemail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jaime Casanova <jaime(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: DELETE with LIMIT (or my first hack)
Date: 2010-12-01 01:57:56
Message-ID: 201012010157.oB11vuk07071@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Daniel Loureiro wrote:
> > 3. This doesn't work tremendously well for inheritance trees, where
> > ModifyTable acts as sort of an implicit Append node.  You can't just
> > funnel all the tuples through one Sort or Limit node because they aren't
> > all the same rowtype.  (Limit might perhaps not care, but Sort will.)
> > But you can't have a separate Sort/Limit for each table either, because
> > that would give the wrong behavior.  Another problem with funneling all
> > the rows through one Sort/Limit is that ModifyTable did need to know
> > which table each row came from, so it can apply the modify to the right
> > table.
> 
> So I guess that I have choose the wrong hack to start.
> 
> Just for curiosity, why the result of "WHERE" filter (in
> SELECT/DELETE/UPDATE) is not put in memory, i.e. an array of ctid, like an
> buffer and then executed by SELECT/DELETE/UPDATE at once ?

Informix dbaccess would prompt a user for confirmation if it saw a
DELETE with no WHERE.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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