Horton

Re: Virtual generated columns

Alexander Lakhin <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Peter Eisentraut <peter@eisentraut.org>, Dean Rasheed <dean.a.rasheed@gmail.com>, jian he <jian.universality@gmail.com>, Zhang Mingli <zmlpostgres@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-05-16T04:00:01Z
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. Expand virtual generated columns for ALTER COLUMN TYPE

  2. Eliminate code duplication in replace_rte_variables callbacks

  3. Expand virtual generated columns in the planner

  4. Virtual generated columns

  5. Additional tests for stored generated columns

  6. Improve generated_stored test

  7. Fix handling of CREATE DOMAIN with GENERATED constraint syntax

  8. Add pg_constraint rows for not-null constraints

  9. Put generated_stored test objects in a schema

  10. Rename regress test generated to generated_stored

  11. Small code simplification

  12. Remove useless code

  13. Remove useless initializations

  14. doc: Clarify that pg_attrdef also stores generation expressions

  15. Clean out column-level pg_init_privs entries when dropping tables.

  16. Re-implement the ereport() macro using __VA_ARGS__.

Hello Richard,

22.02.2025 16:55, Richard Guo wrote:
> create table t (a int, b int);
> create table vt (a int, b int generated always as (a * 2));
>
> insert into t values (1, 1);
> insert into vt values (1);
>
> # select 1 from t t1 where exists
>     (select 1 from vt where exists
>      (select t1.a from t t2 where vt.b = 2));
> ERROR:  unexpected virtual generated column reference

I've discovered yet another way to trigger that error:
create table vt (a int, b int generated always as (a * 2), c int);
insert into vt values(1);
alter table vt alter column c type bigint using b + c;

ERROR:  XX000: unexpected virtual generated column reference
LOCATION:  CheckVarSlotCompatibility, execExprInterp.c:2410

Shouldn't this be expected/supported?

Best regards,
Alexander Lakhin
Neon (https://neon.tech)