Re: Virtual generated columns

Peter Eisentraut <peter@eisentraut.org>

From: Peter Eisentraut <peter@eisentraut.org>
To: jian he <jian.universality@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>, Dean Rasheed <dean.a.rasheed@gmail.com>
Date: 2025-01-08T16:25:07Z
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__.

On 03.12.24 15:15, jian he wrote:
> -- check constraints
> CREATE TABLE gtest20 (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a
> * 2) VIRTUAL CHECK (b < 50));
> INSERT INTO gtest20 (a) VALUES (10);  -- ok
> INSERT INTO gtest20 (a) VALUES (30);  -- violates constraint
> 
> ALTER TABLE gtest20 ALTER COLUMN b SET EXPRESSION AS (a * 100);  --
> violates constraint
> ALTER TABLE gtest20 ALTER COLUMN b SET EXPRESSION AS (a * 3);  -- ok
> -----
> The above content is in src/test/regress/sql/generated_virtual.sql,
> the last two query comments
> seem to conflict with the error message for now.

Fixed the comment in the test in patch v11.

> i add some regress tests for your v10 changes in
> src/backend/commands/statscmds.c.
> please check attached.

Added to patch v11.

> the sql tests,
> "sanity check of system catalog" maybe place it to the end of the sql
> file will have better chance of catching some error.
> for virtual, we can also check attnotnull, atthasdef value.
> like:
> SELECT attrelid, attname, attgenerated FROM pg_attribute WHERE
> attgenerated IN ('v') and (attnotnull or not atthasdef);

I moved the existing check to the bottom, as you suggest.

I don't understand what the purpose of testing attnotnull is.  That is 
independent of attgenerated, I think.