Re: Virtual generated columns

Peter Eisentraut <peter@eisentraut.org>

From: Peter Eisentraut <peter@eisentraut.org>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: jian he <jian.universality@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2024-09-30T02:09:22Z
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__.

Attachments

On 09.09.24 08:02, Peter Eisentraut wrote:
> On 04.09.24 12:33, Dean Rasheed wrote:
>>> I left the 0001 patch alone for now and put the new rewriting
>>> implementation into 0002.  (Unfortunately, the diff is kind of useless
>>> for visual inspection.)  Let me know if this matches what you had in
>>> mind, please.  Also, is this the right place in fireRIRrules()?
>> Yes, that's what I had in mind except that it has to be called from
>> the second loop in fireRIRrules(), after any RLS policies have been
>> added, because it's possible for a RLS policy expression to refer to
>> virtual generated columns. It's OK to do it in the same loop that
>> expands RLS policies, because such policies can only refer to columns
>> of the same relation, so once the RLS policies have been expanded for
>> a given relation, nothing else should get added to the query that can
>> refer to columns of that relation, at that query level, so at that
>> point it should be safe to expand virtual generated columns.
> 
> If I move the code like that, then the postgres_fdw test fails.  So 
> there is some additional interaction there that I need to study.

This was actually a trivial issue.  The RLS loop skips relation kinds 
that can't have RLS policies, which includes foreign tables.  So I did 
this slightly differently and added another loop below the RLS loop for 
the virtual columns.  Now this all works.

I'm attaching a consolidated patch here, so we have something up to date 
on the record.  I haven't worked through all the other recent feedback 
from Jian He yet; I'll do that next.