Skip site navigation (1) Skip section navigation (2)

Re: BUG #5611: SQL Function STABLE promoting to VOLATILE

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Brian Ceccarelli <bceccarelli(at)net32(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "pgsql-bugs(at)postgresql(dot)org" <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: BUG #5611: SQL Function STABLE promoting to VOLATILE
Date: 2010-08-11 21:49:51
Message-ID: AANLkTikcqAVqBY449+HWsYx7cP_pzuTgEnB5ZhFh5hbD@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-bugs
On Wed, Aug 11, 2010 at 4:47 PM, Brian Ceccarelli <bceccarelli(at)net32(dot)com> wrote:
> Please show me an example where an inline query gets a performance boost.

Sure.

rhaas=# create table example as select a from
generate_series(1,100000) a;      SELECT 100000
rhaas=# alter table example add primary key (a);
NOTICE:  ALTER TABLE / ADD PRIMARY KEY will create implicit index
"example_pkey" for table "example"
ALTER TABLE
rhaas=# create function f() returns setof int as $$select a from
example$$ language sql stable;
rhaas=# explain analyze select * from f() where f = 1;
                                                               QUERY
PLAN
----------------------------------------------------------------------------------------------------------------------
 Index Scan using example_pkey on example  (cost=0.00..8.28 rows=1
width=4) (actual time=0.102..0.103 rows=1 loops=1)
   Index Cond: (a = 1)
 Total runtime: 0.149 ms
(3 rows)
rhaas=# alter function f() volatile;
ALTER FUNCTION
rhaas=# explain analyze select * from f() where f = 1;
                                            QUERY PLAN
---------------------------------------------------------------------------------------------------
 Function Scan on f  (cost=0.25..12.75 rows=5 width=4) (actual
time=34.585..51.972 rows=1 loops=1)
   Filter: (f = 1)
 Total runtime: 63.277 ms
(3 rows)

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company

In response to

pgsql-bugs by date

Next:From: Robert HaasDate: 2010-08-12 00:28:03
Subject: Re: BUG #5588: I use a lot of the "INHERITS", results of tests found that the performance is very low.
Previous:From: Alvaro HerreraDate: 2010-08-11 21:25:11
Subject: Re: BUG #5611: SQL Function STABLE promoting to VOLATILE

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group