Re: multicolumn indexes still efficient if not fully stressed?

Jörg Kiegeland <kiegeland(at)ikv(dot)de> schrieb:

> Hello,
>
> I created a multicolumn index on the columns c_1,..,c_n .
> If I do use only a true subset of these columns in a SQL query, is the
> index still efficient?
> Or is it better to create another multicolumn index defined on this subset?

Create several indexes for each column, since 8.1 PG can use a so called
Bitmap Index Scan. Read more about that:

- http://www.postgresql-support.de/pgbook/node492.html
(in german, i think, you can read that)

- http://en.wikipedia.org/wiki/Bitmap_index

Andreas
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