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Date: Thu, 16 Sep 2004 12:39:04 +0200
From: Markus Schaber <schabios@logi-track.com>
To: ischamay.andbergsay@activestateway.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Data Warehouse Reevaluation - MySQL vs Postgres --
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Hi, Mischa,

On Tue, 14 Sep 2004 22:58:20 GMT
Mischa Sandberg <ischamay.andbergsay@activestateway.com> wrote:

> Googling 'upsert' (an Oraclism, I believe) will get you hits on Oracle=20
> and DB2's implementation of MERGE, which does what AMOUNTS to what is
> described below (one mass UPDATE...FROM, one mass INSERT...WHERE NOT=20
> EXISTS).
>=20
> No, you shouldn't iterate row-by-row through the temp table.
> Whenever possible, try to do updates in one single (mass) operation.
> Doing it that way gives the optimizer the best chance at amortizing
> fixed costs, and batching operations.

But when every updated row has a different value for the column(s) to be
updated, then I still have to use one update statement per row, which I
expect to be faster when done via a stored procedure than having the
whole client-server roundtrip including parsing every time. Or did I
miss some nice SQL statement?


Have a nice day,
Markus
--=20
markus schaber | dipl. informatiker
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