Index and performance

From: Andreas Schlegel <schlegelaw(at)gmx(dot)de>
To: pgsql-general(at)postgresql(dot)org
Subject: Index and performance
Date: 2002-12-15 21:45:49
Message-ID: 3DFCF80D.3080505@gmx.de
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Hi,

to get the best query performance is it necessary to create a separate
index on a column which is already part of an another index?

Example:

Table TEST:
COL1
COL2
COL3

The PRIMARY KEY consists of COL1 and COL2. But if I run a query only on
the not unique COL1 is it better for the query performance to have a
separate index or is the existence of the primary key sufficient?

Greetings,
Andreas

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