Re: INSERT OU UPDATE WITHOUT SELECT?

From: "D'Arcy J(dot)M(dot) Cain" <darcy(at)druid(dot)net>
To: "Dave Dutcher" <dave(at)tridecap(dot)com>
Cc: lists(at)peufeu(dot)com, pgsql-performance(at)postgresql(dot)org
Subject: Re: INSERT OU UPDATE WITHOUT SELECT?
Date: 2006-05-30 23:05:08
Message-ID: 20060530190508.aa47bafe.darcy@druid.net
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On Tue, 30 May 2006 17:54:00 -0500
"Dave Dutcher" <dave(at)tridecap(dot)com> wrote:
> What I do when I'm feeling lazy is execute a delete statement and then
> an insert. I only do it when I'm inserting/updating a very small number
> of rows, so I've never worried if its optimal for performance. Besides
> I've heard that an update in postgres is similar in performance to a
> delete/insert.

Well, they are basically the same operation in PostgreSQL. An update
adds a row to the end and marks the old one dead. A delete/insert
marks the row dead and adds one at the end. There may be some
optimization if the engine does both in one operation.

--
D'Arcy J.M. Cain <darcy(at)druid(dot)net> | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
+1 416 425 1212 (DoD#0082) (eNTP) | what's for dinner.

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