Re: Expression indexes and dependecies

On Mon, Jul 22, 2013 at 6:04 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Pavan Deolasee escribió:
>> Hello,
>>
>> While doing some tests, I observed that expression indexes can malfunction
>> if the underlying expression changes.
>
> [...]
>
>> Perhaps this is a known behaviour/limitation, but I could not find that in
>> the documentation. But I wonder if it makes sense to check for dependencies
>> during function alteration and complain. Or there are other reasons why we
>> can't do that and its a much larger problem than what I'm imagining ?
>
> This is a tough problem.  The dependency mechanism has no way to keep
> track of this kind of dependency; all it does is prevent the function
> from being dropped altogether, but preventing it from acquiring a
> conflicting definition is outside its charter.
>
> 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.

What about a warning and leave it to the dba to reindex?