From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Expression indexes and dependecies |
Date: | 2013-07-22 23:21:35 |
Message-ID: | 28815.1374535295@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2013-07-22 17:04:06 -0400, Alvaro Herrera wrote:
>> One way to attack this would be registering dependencies of a new kind
>> on functions used by index expressions. Then CREATE OR REPLACE function
>> could reject alteration for such functions. I don't know if we care
>> enough about this case.
> I think changing the results of a immutable function violates the
> contract enough to make this the user's fault. Also the other solutions
> seem hard to achieve ;)
Yeah. Prohibiting any change at all would be a cure worse than the
disease, likely, but we don't have the tools to analyze more finely than
that. And what if the index uses function A which calls function B,
and you change function B?
I'd be in favor of adding a note to the CREATE INDEX man page pointing
out that if you change the behavior of an immutable function, any bad
consequences for indexes are on your own head, and a REINDEX would be
advisable.
regards, tom lane
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