From: | "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com> |
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To: | <pgsql-performance(at)postgresql(dot)org> |
Subject: | Quesion on the use of indexes |
Date: | 2010-08-17 03:22:57 |
Message-ID: | F4E6A2751A2823418A21D4A160B689887B0362@fletch.stackdump.local |
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Lists: | pgsql-performance |
A little background - I have various multi-column indexes whenever I
have queries which restrict the output based on the values of the 2
fields (for example, a client code and the date of a transaction).
Is there a performance gain using this approach as opposed to using 2
separate indexes, one on the first column and one on the second column?
The reason I am asking is that my coding convetion goes back to the days
where I used ISAM tables, so the systems did not know how to use more
than a single index.
In some cases, I may have an index on (columna, columnb) and one on
(columnb, columna) due to the data access patterns. If there are no
performance gains in having these multi-part indexes, and performance
will be the same as having one index solely on columna and one solely on
columnb, then I can reduce the disk usage significantly in some cases.
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