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

Tom Lane írta:
> Zoltan Boszormenyi <zb@cybertec.at> writes:
>
>> 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.
>>
>
> Sounds good.
>

Finally here it is.

>> 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.
>>
>
> Is there any good reason to distinguish the two?
>

Actually, I needed to have a flag for IDENTITY
but not for the reason above. I need it to distinguish
between GENERATED ALWAYS AS IDENTITY
and GENERATED ALWAYS AS ( expr ).

Changes:
- Rewritten the GENERATED/IDENTITY flags to be part of the default
pg_attrdef
   This made the patch MUCH smaller.
- SERIALs are now the same as INTEGER GENERATED BY DEFAULT AS IDENTITY
- Allow DROP DEFAULT on GENERATED/IDENTITY columns
- Implemented SET GENERATED ALWAYS AS
- Modified syntax of SET GENERATED {ALWAYS | BY DEFAULT} AS IDENTITY
    so it reads as SET IDENTITY GENERATED {ALWAYS | BY DEFAULT}
    so compiling gram.y/gram.c doesn't give me errors.
    This DDL statement isn't part of SQL:2003 so it might be accepted
    as a PostgreSQL extension.
- Modified behaviour of SET IDENTITY to also restore the DEFAULT
    expression. Someone might have done did a DROP DEFAULT before
    but kept the OWNED sequence.
- Fixed behaviour of GENERATED columns regarding
    INSERT ... OVERRIDING SYSTEM VALUE and
    only those GENERATED columns get UPDATEd that
    are either explicitly modified with SET column = DEFAULT
    or one of their referenced columns are modified.
- Testcase and documentation is modified to reflect the above.

Please, review.

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