Re: Unused Indexes

Assuming you have done a 'VACUUM ANALYZE' on the table in question you
are most likely running into a type coercion issue.
So explicitly cast your constants to bigint and the index should start
being considered.

select id from <table> where col2 = 1::bigint and col2 = 1::bigint

Tim McAuley wrote:

> Hi,
>
> I have a table which I have populated with over 5000 entries. There is
> a combined index placed on two of the columns (both bigint). I am
> trying a simple select (i.e. select id where col1 = 1 and col2 = 1)
> covering these two columns and it keeps using a seq scan. Is this
> correct? I would have thought that with this number of entries that an
> index scan should be used.
>
> I am testing this using postgresql 7.3.3 on windows 2000 using cygwin.
>
> Doing "set enable_seqscan to off" does not change the results of the
> explain operation.
>
> I also tried setting a single index on just one of the columns and
> running an appropriate search; it still uses a seq scan. At what stage
> will the planner normally start using an index scan?
>
> Any hints appreciated.
>
> Tim
>
>
>
>
>
>
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