Re: UUID index unused

This affirmation that it indeed does work set me straight. I inadvertently made a previously immutable UUID function volatile; it was providing the UUIDs in the query.

> On Nov 9, 2014, at 2:12 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Kevin Wooten <kdubb(at)me(dot)com> writes:
>> I am assuming I am crazy and missing something completely obvious but I cannot get postgres (9.3.5) to use an index on a UUID, ever.
>
> Worksforme:
>
> regression=# create table foo (f1 uuid primary key);
> CREATE TABLE
> regression=# explain select * from foo where f1 = 'a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11';
> QUERY PLAN
> --------------------------------------------------------------------------
> Index Only Scan using foo_pkey on foo (cost=0.15..8.17 rows=1 width=16)
> Index Cond: (f1 = 'a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11'::uuid)
> (2 rows)
>
>> The main table has a natural composite key (2 uuids and a timestamp) with which it always uses the timestamp as the index condition and filters on the UUIDs.
>
> This probably has little to do with the datatype as such, and much to do
> with the specifics of your query, the available indexes, and the table's
> statistics. It's hard to speculate further without lots more detail
> about those things.
>
> regards, tom lane