From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | andipeer(at)gmx(dot)net, pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #4421: convert_to() should be immutable |
Date: | 2008-09-17 17:46:55 |
Message-ID: | 20831.1221673615@sss.pgh.pa.us |
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Lists: | pgsql-bugs |
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> andipeer(at)gmx(dot)net wrote:
>> 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".
> You can change the way a conversion is done with CREATE/DROP CONVERSION.
> That's why it can't be IMMUTABLE.
The other reason is that it depends on the database encoding. I suppose
you could make an argument that that's fixed for as long as IMMUTABLE
needs to think about --- but we'd have to remember to undo the marking
if database encoding ever becomes less fixed.
Just out of curiosity, what's the use-case for this function in an index
anyway?
regards, tom lane
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