Tom Lane wrote:
>"Wang Mike" <itlist@msn.com> writes:
>
>
>>but this query: select * from test_uuid where id =
>>'df2b10aa-a31d-11d7-9867-0050babb6029'::uuid dosn't use index
>>
>>
>
>
>
>> QUERY PLAN
>>---------------------------------------------------------------
>> Seq Scan on test_uuid (cost=0.00..22.50 rows=500 width=140)
>> Filter: (id = 'df2b10aa-a31d-11d7-9867-0050babb6029'::uuid)
>>
>>
>
>
>
>>why ??
>>
>>
>
>The rows estimate looks pretty fishy --- I think you are getting the
>0.5 default selectivity estimate for an operator that has no restriction
>estimator. Most likely you should have created the operator using eqsel
>and eqjoinsel as the restriction/join estimators.
>
> regards, tom lane
>
>
>
Hi, Tom,
I'm trying to test it, but don't know if I understood you correctly, you mean we should try to create the
operatorusing
eqsel/eqjoinsel estimators, right? But after we added those estimators like this:
CREATE OPERATOR = ( LEFTARG = uuid, RIGHTARG = uuid, COMMUTATOR = =, NEGATOR = <>, PROCEDURE = uuid_eq,
RESTRICT= eqsel, JOIN = eqjoinsel
);
the situation trun worse: now the explain shows the query using the
index, the we can't select out the match row! Any hint about what's wrong
with us?
Thanks and Reagards
Laser
