Horton

Re: ALTER COLUMN ... SET EXPRESSION to alter stored generated column's expression

amul sul <sulamul@gmail.com>

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From: Amul Sul <sulamul@gmail.com>
To: Peter Eisentraut <peter@eisentraut.org>
Cc: Robert Haas <robertmhaas@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Vaibhav Dalvi <vaibhav.dalvi@enterprisedb.com>, pgsql-hackers@postgresql.org
Date: 2023-11-14T10:40:04Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. ALTER TABLE command to change generation expression

  2. Refactor: separate function to find all objects depending on a column

  3. Turn AT_PASS_* macros into an enum

Attachments

On Mon, Nov 13, 2023 at 9:09 PM Peter Eisentraut <peter@eisentraut.org>
wrote:

> On 13.11.23 14:07, Amul Sul wrote:
> >     Also, it seems to me that the SET EXPRESSION variant should just do
> an
> >     update of the catalog table instead of a drop and re-insert.
> >
> > I am not sure if that is sufficient; we need to get rid of the
> > dependencies of
> > existing expressions on other columns and/or objects that need to be
> > removed.
> > The drop and re-insert does that easily.
>
> Ok, good point.
>
> >     The documentation needs some improvements:
> >
> >     +    ALTER [ COLUMN ] <replaceable
> >     class="parameter">column_name</replaceable> SET EXPRESSION
> <replaceable
> >     class="parameter">expression</replaceable> STORED
> >
> >     If we're going to follow the Db2 syntax, there should be an "AS"
> after
> >     EXPRESSION.  And the implemented syntax requires parentheses, so they
> >     should appear in the documentation.
> >
> >     Also, the keyword STORED shouldn't be there.  (The same command
> should
> >     be applicable to virtual generated columns in the future.)
> >
> > I have omitted "AS" intentionally, to keep syntax similar to our existing
> > ALTERCOLUMN... SET DEFAULT <a_expr>.  Let me know if you want
> > me to add that.
>
> Well, my idea was to follow the Db2 syntax.  Otherwise, we are adding
> yet another slightly different syntax to the world.  Even if we think
> our idea is slightly better, it doesn't seem worth it.
>

Ok.

Please have a look at the attached version, updating the syntax to have "AS"
after EXPRESSION and other changes suggested previously.

Regards,
Amul