Horton

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

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: Amul Sul <sulamul@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Vaibhav Dalvi <vaibhav.dalvi@enterprisedb.com>, pgsql-hackers@postgresql.org
Date: 2023-12-18T09:31:03Z
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

On 11.12.23 13:22, Amul Sul wrote:
> 
>     create table t1 (a int, b int generated always as (a + 1) stored);
>     alter table t1 add column c int, alter column b set expression as (a
>     + c);
>     ERROR:  42703: column "c" does not exist
> 
>     I think intuitively, this ought to work.  Maybe just moving the new
>     pass
>     after AT_PASS_ADD_COL would do it.
> 
> 
> I think we can't support that (like alter type) since we need to place 
> this new
> pass before AT_PASS_OLD_INDEX & AT_PASS_OLD_CONSTR to re-add indexes and
> constraints for the validation.

Could we have AT_PASS_ADD_COL before AT_PASS_OLD_*?  So overall it would be

...
AT_PASS_ALTER_TYPE,
AT_PASS_ADD_COL,         // moved
AT_PASS_SET_EXPRESSION,  // new
AT_PASS_OLD_INDEX,
AT_PASS_OLD_CONSTR,
AT_PASS_ADD_CONSTR,
...

This appears to not break any existing tests.