Re: Question about a CIDR based query

Hello,

Consider that I have the following table:

Create Table tmp(
            route_id     int    NOT NULL,
            route         cidr   NOT NULL,
            Data         varchar(100) NOT NULL)

The table contains ~40,000 routes and I have an index on route.

The query I am interested in is:

select * from tmp where route >>= some_cidr

The index on route is not used and I get a sequential scan. The index is
used only for the <<= operator.

Any idea how I can make the query run faster?

Thanks,
George

Georgos,

> select * from tmp where route >>= some_cidr

Can you post an EXPLAIN ANALYZE for this? And when's the last time you ran
ANALYZE on the table?

> The index on route is not used and I get a sequential scan. The index is
> used only for the <<= operator.

Most likely Postgres thinks that the >>= query is returning 60% of your table,
which makes indexes useless.

--
Josh Berkus
Aglio Database Solutions
San Francisco

I did a vacuum analyze before I run the following explain

June_03=# explain select * from tmp where route >>='62.1.1.0/24';
QUERY PLAN
----------------------------------------------------------------
Seq Scan on tmp (cost=0.00..606.60 rows=14544 width=33)
Filter: (route >>= '62.1.1.0/24'::cidr)
(2 rows)

The select returns just one route,
Thanks

josh(at)agliodbs(dot)com (Josh Berkus) wrote in message news:<200406250900(dot)08312(dot)josh(at)agliodbs(dot)com>...
> Georgos,
>
> > select * from tmp where route >>= some_cidr
>
> Can you post an EXPLAIN ANALYZE for this? And when's the last time you ran
> ANALYZE on the table?
>
> > The index on route is not used and I get a sequential scan. The index is
> > used only for the <<= operator.
>
> Most likely Postgres thinks that the >>= query is returning 60% of your table,
> which makes indexes useless.
>
> --
> Josh Berkus
> Aglio Database Solutions
> San Francisco
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/docs/faqs/FAQ.html

George,

Um, no, I need an EXPLAIN ANALYZE, not just an EXPLAIN. Thanks.

> June_03=# explain select * from tmp where route >>='62.1.1.0/24';
> QUERY PLAN
> ----------------------------------------------------------------
> Seq Scan on tmp (cost=0.00..606.60 rows=14544 width=33)
> Filter: (route >>= '62.1.1.0/24'::cidr)

--
-Josh Berkus
Aglio Database Solutions
San Francisco

George,

> Um, no, I need an EXPLAIN ANALYZE, not just an EXPLAIN. Thanks.
>
> > June_03=# explain select * from tmp where route >>='62.1.1.0/24';
> > QUERY PLAN
> > ----------------------------------------------------------------
> > Seq Scan on tmp (cost=0.00..606.60 rows=14544 width=33)
> > Filter: (route >>= '62.1.1.0/24'::cidr)

Oh, and also a SELECT VERSION(); would be nice.

--
Josh Berkus
Aglio Database Solutions
San Francisco

Hi Josh,
Ok, first the explain analyze ....

June_03=# explain analyze select * from tmp where route
>>='62.1.1.0/24';
QUERY PLAN
-----------------------------------------------------------------------------------------------------------
Seq Scan on tmp (cost=0.00..606.60 rows=14544 width=33) (actual
time=3.862..15.366 rows=1 loops=1)
Filter: (route >>= '62.1.1.0/24'::cidr)
Total runtime: 15.493 ms
(3 rows)

And the version of postgres

June_03=# select version();
version
--------------------------------------------------------------------------------------------------------------------
PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
3.3.2 20031022 (Gentoo Linux 3.3.2-r2, propolice)
(1 row)

Thanks,
Georgos

josh(at)agliodbs(dot)com (Josh Berkus) wrote in message news:<200406292049(dot)06283(dot)josh(at)agliodbs(dot)com>...
> George,
>
> > Um, no, I need an EXPLAIN ANALYZE, not just an EXPLAIN. Thanks.
> >
> > > June_03=# explain select * from tmp where route >>='62.1.1.0/24';
> > > QUERY PLAN
> > > ----------------------------------------------------------------
> > > Seq Scan on tmp (cost=0.00..606.60 rows=14544 width=33)
> > > Filter: (route >>= '62.1.1.0/24'::cidr)
>
> Oh, and also a SELECT VERSION(); would be nice.