Re: BUG: PG do not use index

In response to Eugen.Konkov@aldec.com:

> Why PG do not use index?

The standard question: when was the last time you did a vacuum analyze
on this table?

>
> select max(id) from akh_testing_result
> For MySQL this query take 2-3ms, but Postgres take 132 000ms to execute query.
>
> select max(id) from akh_testing_result
> Query executed in 2,12 minutes, 1 Record(s) Returned
> --------------------------------------------------------------------
> max
> ---------------
> 8757173
>
> As we see table has about 9 000 000 records
>
> EXPLAIN select max(id) from akh_testing_result
> "Aggregate  (cost=204986.95..204986.95 rows=1 width=4)"
> "  ->  Seq Scan on akh_testing_result  (cost=0.00..183568.56 rows=8567356 width=4)"
>
> Notice that 'id' field is primary index
>
> -- DROP TABLE public.akh_testing_result;
> CREATE TABLE public.akh_testing_result
> (
> id serial NOT NULL,
> testing_conf_id integer NOT NULL,
> name varchar(64) NOT NULL,
> test_group_id integer NOT NULL,
> test_status_id integer NOT NULL,
> comment text,
> bug_commited boolean,
> best_testing_conf_id integer,
> best_testing_conf_name varchar(255),
> test_time integer,
> physical_memory_peak integer,
> virtual_memory_peak integer,
> test_id integer,
> CONSTRAINT "akh_testing_result_pkey" PRIMARY KEY (id),
> CONSTRAINT "akh_testing_result_testing_conf_fkey" FOREIGN KEY (testing_conf_id) REFERENCES akh_testing_conf(id) ON
UPDATERESTRICT ON DELETE RESTRICT, 
> CONSTRAINT "akh_testing_result_test_group_fkey" FOREIGN KEY (test_group_id) REFERENCES akh_test_group(id) ON UPDATE
RESTRICTON DELETE RESTRICT, 
> CONSTRAINT "akh_testing_result_test_status_fkey" FOREIGN KEY (test_status_id) REFERENCES akh_properties(id) ON UPDATE
RESTRICTON DELETE RESTRICT, 
> CONSTRAINT "akh_testing_result_test_fkey" FOREIGN KEY (test_id) REFERENCES akh_test(id) ON UPDATE RESTRICT ON DELETE
RESTRICT
> );
> -- Indexes
> CREATE INDEX akh_testing_result_testing_conf ON akh_testing_result USING btree (testing_conf_id);
> -- Owner
> ALTER TABLE public.akh_testing_result OWNER TO postgres;
>
>
>
>
>
>


--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023

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