Re: IDENTITY/GENERATED v36 Re: Final version of IDENTITY/GENERATED patch

Tom Lane írta:
> Zoltan Boszormenyi <zb@cybertec.at> writes:
>
>> I have two questions about the dependency system.
>>
>
>
>> 1. Is there a built-in defense to avoid circular dependencies?
>>
>
> It doesn't have a problem with them, if that's what you mean.
>
>
>> 2. If I register dependencies between column, is there a way
>>     to retrieve all table/column type dependencies for a depender column?
>>
>
> You can scan pg_depend.
>
>
>> What I would like to achieve is to lift the limit that
>> a GENERATED column cannot reference another one.
>>
>
> I would counsel not doing that, mainly because then you will have to
> solve an evaluation-order problem at runtime.
>

OK.

>> Point taken. So, just like with SET / DROP IDENTITY,
>> I should implement SET GENERATED ALWAYS
>> and DROP GENERATED.
>>
>
> If you think of it as a property of the default expression, then DROP
> DEFAULT covers both cases, you don't need DROP GENERATED...
>

So, I should allow DROP DEFAULT, implement
SET DEFAULT GENERATED ALWAYS AS
and modify the catalog so the GENERATED property
is part of pg_attrdef. What about IDENTITY?
Should it also be part of pg_attrdef? There are two ways
to implement it: have or don't have a notion of it.
The latter would treat GENERATED BY DEFAULT AS IDENTITY
the same as SERIAL.

>             regards, tom lane
>

--
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Zoltán Böszörményi
Cybertec Geschwinde & Schönig GmbH
http://www.postgresql.at/