Optimizing query

Do something like:

CREATE OR REPLACE FUNCTION my_date_part( timestamp) RETURNS DOUBLE precision AS '
DECLARE
mydate ALIAS FOR $1;
BEGIN
return date_part( ''day'', mydate );
END;' LANGUAGE 'plpgsql' IMMUTABLE;

create index idx_tmp on stat_views( my_date_part( created ) );

or add an extra date_part column to your table which pre-calculates date_part('day', created) and put an index on this.

Cheers
Matthew
--

----- Original Message -----
From: Uros
To: pgsql-general@postgresql.org
Sent: Wednesday, November 19, 2003 10:41 AM
Subject: [GENERAL] Optimizing query

Hello!

I have some trouble getting good results from my query.

here is structure

stat_views
id | integer
id_zone | integer
created | timestamp

I have btree index on created and also id and there is 1633832 records in
that table

First of all I have to manualy set seq_scan to OFF because I always get
seq_scan. When i set it to off my explain show:

explain SELECT count(*) as views FROM stat_views WHERE id = 12;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Aggregate (cost=122734.86..122734.86 rows=1 width=0)
-> Index Scan using stat_views_id_idx on stat_views (cost=0.00..122632.60 rows=40904 width=0)
Index Cond: (id = 12)

But what I need is to count views for some day, so I use

explain SELECT count(*) as views FROM stat_views WHERE date_part('day', created) = 18;

QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984 width=0)
Filter: (date_part('day'::text, created) = 18::double precision)

How can I make this to use index and speed the query. Now it takes about 12
seconds.

--
Best regards,
Uros mailto:uros@sir-mag.com

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Uros writes:

explain SELECT count(*) as views FROM stat_views WHERE date_part('day', created) = 18;

QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984 width=0)
Filter: (date_part('day'::text, created) = 18::double precision)

Create an index on date_part('day', created). In 7.3 and earlier you need
to create a wrapper function and index that, in 7.4 you can index
arbitrarz expressions directly. The documentation contains more
information about that.

--
Peter Eisentraut peter_e@gmx.net

Uros wrote:

Hello!

I have some trouble getting good results from my query.

here is structure

stat_views
id | integer
id_zone | integer
created | timestamp

I have btree index on created and also id and there is 1633832 records in
that table

First of all I have to manualy set seq_scan to OFF because I always get
seq_scan. When i set it to off my explain show:

explain SELECT count(*) as views FROM stat_views WHERE id = 12;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Aggregate (cost=122734.86..122734.86 rows=1 width=0)
-> Index Scan using stat_views_id_idx on stat_views (cost=0.00..122632.60 rows=40904 width=0)
Index Cond: (id = 12)

But what I need is to count views for some day, so I use

explain SELECT count(*) as views FROM stat_views WHERE date_part('day', created) = 18;

QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984 width=0)
Filter: (date_part('day'::text, created) = 18::double precision)

How can I make this to use index and speed the query. Now it takes about 12
seconds.

Can you post explain analyze for the same?

Shridhar

Hello Shridhar,

I use Matthew's solution and it works. Query takes only half a second. I
didn't know that i can index function to.

Thanks

Uros

Wednesday, November 19, 2003, 1:23:26 PM, you wrote:

SD> Uros wrote:

Hello!

I have some trouble getting good results from my query.

here is structure

stat_views
id | integer
id_zone | integer
created | timestamp

I have btree index on created and also id and there is 1633832 records in
that table

First of all I have to manualy set seq_scan to OFF because I always get
seq_scan. When i set it to off my explain show:

explain SELECT count(*) as views FROM stat_views WHERE id = 12;
QUERY PLAN
----------------------------------------------------------------------------------------------------
Aggregate (cost=122734.86..122734.86 rows=1 width=0)
-> Index Scan using stat_views_id_idx on stat_views
(cost=0.00..122632.60 rows=40904 width=0)
Index Cond: (id = 12)

But what I need is to count views for some day, so I use

explain SELECT count(*) as views FROM stat_views WHERE date_part('day', created) = 18;

QUERY PLAN
------------------------------------------------------------------------------------
Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984 width=0)
Filter: (date_part('day'::text, created) = 18::double precision)

How can I make this to use index and speed the query. Now it takes about 12
seconds.

SD> Can you post explain analyze for the same?

SD> Shridhar

Greetings all,

Yesterday I upgraded from 7.3 to 7.4 now psql doesn't work! I get the
following error.

psql: relocation error: psql: undefined symbol: get_progname

Any ideas out there?

Rob

-----Original Message-----
From: pgsql-general-owner@postgresql.org
[mailto:pgsql-general-owner@postgresql.org] On Behalf Of Shridhar Daithankar
Sent: Wednesday, November 19, 2003 6:23 AM
To: Uros
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Optimizing query

Uros wrote:

Hello!

I have some trouble getting good results from my query.

here is structure

stat_views
id | integer
id_zone | integer
created | timestamp

I have btree index on created and also id and there is 1633832 records in
that table

First of all I have to manualy set seq_scan to OFF because I always get
seq_scan. When i set it to off my explain show:

explain SELECT count(*) as views FROM stat_views WHERE id = 12;
QUERY PLAN

----------------------------------------------------------------------------
------------------------

Aggregate (cost=122734.86..122734.86 rows=1 width=0)
-> Index Scan using stat_views_id_idx on stat_views

(cost=0.00..122632.60 rows=40904 width=0)

Index Cond: (id = 12)

But what I need is to count views for some day, so I use

explain SELECT count(*) as views FROM stat_views WHERE date_part('day',

created) = 18;

QUERY PLAN

----------------------------------------------------------------------------
--------

Aggregate (cost=100101618.08..100101618.08 rows=1 width=0)
-> Seq Scan on stat_views (cost=100000000.00..100101565.62 rows=20984

width=0)

Filter: (date_part('day'::text, created) = 18::double precision)

How can I make this to use index and speed the query. Now it takes about

12

seconds.

Can you post explain analyze for the same?

Shridhar

---------------------------(end of broadcast)---------------------------
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Rob Sell wrote:

Greetings all,

Yesterday I upgraded from 7.3 to 7.4 now psql doesn't work! I get the
following error.

psql: relocation error: psql: undefined symbol: get_progname

Any ideas out there?

You have an old copy of the library or binaries around somewhere.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073