Message-ID: <43EB18B7.4060006@archonet.com>
Date: Thu, 09 Feb 2006 10:25:59 +0000
From: Richard Huxton <dev@archonet.com>
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To: ken@scottshill.com
Cc: pgsql-sql@postgresql.org
Subject: Re: Column Index vs Record Insert Trade-off?
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Ken Hill wrote:
> Is there a performance trade-off between column indexes and record
> inserts?
> 
> I know that in MS Access there is such a trade-off. This being indexes
> make SQL queries perform faster at the cost of record insert speed. Put
> another way, the more column indexes in a table, the slower a record
> insert in that table performs.
> 
> Is there a similar trade-off in PostgreSQL?

The tradeoff is made in every system. The more indexes you have on a 
table, the more indexes need to be updated when you update/insert/delete 
rows.

So - a unique constraint automatically implies an index in PostgreSQL 
(it's how it implements its unique checks). Other than that, you should 
only index those columns where you will want a small number of rows or 
quick ordering.

-- 
   Richard Huxton
   Archonet Ltd