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Re: function side effects

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Peter Eisentraut" <peter_e(at)gmx(dot)net>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Greg Stark" <gsstark(at)mit(dot)edu>, "Tatsuo Ishii" <ishii(at)postgresql(dot)org>, <pgsql-hackers(at)postgresql(dot)org>, "Jaime Casanova" <jcasanov(at)systemguards(dot)com(dot)ec>
Subject: Re: function side effects
Date: 2010-03-01 23:09:56
Message-ID: 4B8BF4E4020000250002F769@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>> SQL standard:
> 
>> <SQL-data access indication> ::=
>> NO SQL
>> | CONTAINS SQL
>> | READS SQL DATA
>> | MODIFIES SQL DATA
> 
> Huh.  I understand three of those, but what is the use of CONTAINS
> SQL?  Seems like that would have to be the same as the last one,
> or maybe the next-to-last one if you're prepared to assume it's
> read-only SQL.
 
On a quick search of the spec, the best I was able to tell was that
you are required to use "CONTAINS SQL" if the language is SQL. 
Perhaps it figures that the database engine can determine the
read/write behavior directly if the language is SQL, and you tell it
what it does if you're coding in some other language.
 
-Kevin

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