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Re: BUG #4421: convert_to() should be immutable

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: andipeer(at)gmx(dot)net
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #4421: convert_to() should be immutable
Date: 2008-09-17 15:24:03
Message-ID: 48D12113.2000306@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-bugs
andipeer(at)gmx(dot)net wrote:
> PostgreSQL version: 8.3.3
> Operating system:   Linux
> Description:        convert_to() should be immutable
> Details: 
> 
> The function convert_to(string text, dest_encoding name) is not allowed to
> be used in a index expression, because it is not marked as "IMMUTABLE".
> According to the documentation, a function is immutable if it does not
> modify the database, and for the same arguments, it returns always the same
> results. I think that all of these conditions can be applied to the
> convert_to()-function, therefore it should be marked as "IMMUTABLE".

You can change the way a conversion is done with CREATE/DROP CONVERSION. 
That's why it can't be IMMUTABLE.

(I doubt any sane person would actually do that, but that's another debate)

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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