Re: Multiple-index optimization not working for = ANY operator

On 2006-02-15, "Jimmy Choi" <JCHOI(at)altera(dot)com> wrote:
> I find that it doesn't work (i.e. index is not used and a sequential
> scan is needed), if I have the following instead:
>
> SELECT * FROM foo WHERE id = ANY (ARRAY[1,2]);
>
> Is this expected? The reason I would like the last case to work is that
> my plpgsql function takes as input an array of IDs, and so I cannot
> write my query using the first two forms above.
>
> Any idea on how I can get around this is greatly appreciated.

The workaround (for versions 7.4 - 8.1) is:

select * from foo
where id in (select myarray[i]
from generate_series(array_lower(myarray,1),
array_upper(myarray,1)) as s(i));

This typically plans out as a nestloop join with an aggregate over the
function scan as the outer path, and an index lookup on foo.id as the
inner path. Execution times for 8.1 are usually very slightly worse than
the equivalent IN (a,b,c,...) with literal values, but the plan time is
shorter.

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Andrew, Supernews
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