Re: Query not using index

On 12/9/05, Kaloyan Iliev <news1@faith.digsys.bg> wrote:
> Hi all,
>
> I have a problem with a query which doeson't want to use indexes. I
> tried to create different indexes but nothing help. Can anyone suggest
> what index I need.
> This query is executed 1.5Milion times per day and I need it to be veri
> fast. I made my test on 8.0.0 beta but the production database is still
> 7.4.6 so i need suggestions for 7.4.6.
> I will post the table with the indexes and the query plans.
> iplog=# \d croute
>                 Table "public.croute"
>     Column      |           Type           | Modifiers
> -----------------+--------------------------+-----------
>  confid          | integer                  |
>  network         | cidr                     |
>  comment         | text                     |
>  router          | text                     |
>  port            | text                     |
> valid_at        | timestamp with time zone |
>  archived_at     | timestamp with time zone |
> Indexes:
>    "croute_netwo" btree (network) WHERE confid > 0 AND archived_at IS NULL
>    "croute_netwokr_valid_at" btree (network, valid_at)
>    "croute_network" btree (network) WHERE archived_at IS NULL
>    "croute_network_all" btree (network)
>
>
> iplog=# select version();
>                                                   version
> --------------------------------------------------------------------------------------------------------------
>  PostgreSQL 8.0.0beta1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
> 3.3.2 (Mandrake Linux 10.0 3.3.2-6mdk)
> (1 row)
>
> !!!!!!!!!!!!THIS IS THE QUERY!!!!!!!!!!!!!!!!!
> customer=> explain analyze SELECT *
> customer->                                    FROM croute
> customer->                                    WHERE '193.68.0.8/32' <<=
> network AND
> customer->                                          (archived_at is NULL
> OR archived_at > '17-11-2005') AND
> customer->                                          valid_at <
> '1-12-2005'::date AND
> customer->                                          confid > 0;
>
> QUERY PLAN
>
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  Seq Scan on croute  (cost=0.00..441.62 rows=413 width=102) (actual
> time=14.131..37.515 rows=1 loops=1)
>   Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
> NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
> zone)) AND (valid_at < ('2005-12-01'::date)::timestamp with time zone)
> AND (confid > 0))
>  Total runtime: 37.931 ms
> (3 rows)
>
> customer=> select count(*) from croute;
>  count
> -------
>  10066
> (1 row)
> This is the result of the query:
> confid   |    network         | comment | router | port |
> valid_at                 | archived_at |
> -------+---------------+---------+------+----+-------------------------+-----------+
>  19971 | xx.xx.xx.xx/32 | xxxxx   | ?       | ?     |    2005-03-11
> 00:00:00+02 |                  |
> (1 row)
> And last I try to stop the sequance scan but it doesn't help. I suppose
> I don't have the right index.
> iplog=# set enable_seqscan = off;
> SET
> iplog=# explain analyze SELECT *
> iplog-#                                    FROM croute
> iplog-#                                    WHERE '193.68.0.8/32' <<=
> network AND
> iplog-#                                          (archived_at is NULL OR
> archived_at > '17-11-2005') AND
> iplog-#                                          valid_at <
> '1-12-2005'::date AND
> iplog-#                                          confid > 0;
>
> QUERY PLAN
>
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  Seq Scan on croute  (cost=100000000.00..100000780.64 rows=1030
> width=103) (actual time=29.593..29.819 rows=1 loops=1)
>   Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
> NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
> zone)) AND (valid_at < '2005-12-01'::date) AND (confid > 0))
>  Total runtime: 29.931 ms
> (3 rows)
>
> I try creating one last index on all fields but it doesn't help.
> iplog=# CREATE INDEX croute_all on
> croute(network,archived_at,valid_at,confid);
> CREATE INDEX
> iplog=# explain analyze SELECT *
> iplog-#                                    FROM croute
> iplog-#                                    WHERE '193.68.0.8/32' <<=
> network AND
> iplog-#                                          (archived_at is NULL OR
> archived_at > '17-11-2005') AND
> iplog-#                                          valid_at <
> '1-12-2005'::date AND
> iplog-#                                          confid > 0;
>
> QUERY PLAN
>
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  Seq Scan on croute  (cost=100000000.00..100000780.64 rows=1030
> width=103) (actual time=29.626..29.879 rows=1 loops=1)
>   Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
> NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
> zone)) AND (valid_at < '2005-12-01'::date) AND (confid > 0))
>  Total runtime: 30.060 ms
> (3 rows)
>
>
> Thanks in advance to all.
>
> Kaloyan Iliev
>
>

In oracle you can use this instead...

SELECT * FROM croute
WHERE '193.68.0.8/32' <<= network
     AND archived_at is NULL
     AND valid_at < '1-12-2005'::date
     AND confid > 0;
UNION
SELECT * FROM croute
WHERE '193.68.0.8/32' <<= network
     AND archived_at > '17-11-2005'::date
     AND valid_at < '1-12-2005'::date
     AND confid > 0;


although i think that your query can make use of bitmap index in 8.1

--
regards,
Jaime Casanova
(DBA: DataBase Aniquilator ;)