Re: identity columns

On Sun, Apr 23, 2017 at 9:03 PM, Vitaly Burovoy
<vitaly(dot)burovoy(at)gmail(dot)com> wrote:
>> But why do we need it? Instead of:
>>
>> ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY
>> SET GENERATED { ALWAYS | BY DEFAULT }
>> DROP IDENTITY [ IF EXISTS ]
>>
>> Why not just:
>>
>> SET GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY
>> DROP IDENTITY [ IF EXISTS ]
>>
>> Surely the ALTER TABLE command can tell whether the column is already
>> GENERATED, so the first form could make it generated if it's not and
>> adjust the ALWAYS/BY DEFAULT property if it is.
>
> I thought exactly that way, but Peter gave an explanation[1].

That's not really an explanation. Peter says he needs ADD to make
pg_dump, but he doesn't really. He just needs something that adds it,
and augmenting SET to perform ADD if the sequence is not currently
GENERATED would be fine.

--
Robert Haas
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