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From: Ron Mayer <rm_pg@cheapcomplexdevices.com>
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Subject: Re: Indexing an array?
Date: Fri, 09 Sep 2005 16:35:30 -0700
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Silke Trissl wrote:
> As far I could read from the documentation - this should be possible.
> But my question is, is there a kind of index on the array.

If your needs are a bit more modest (say, a few thousands instead of 
billions) the stuff in contrib/intarray works well; and if you
needed types other than integers you can you can look at intarray
to see how to build indexes on them and what those indexes
are useful for.

> Lets say, I want to get element 2,675,345,328. Does Postgres have to
> load the entire array into memory and then run through the 2.6 billion
> characters to return the one I want or does Postgres have an index - as
> where to find this element on disk?

Wouldn't you rather expect an index to be useful for finding which
rows match your query rather than for finding content within a row?