Re: Virtual generated columns

Dean Rasheed <dean.a.rasheed@gmail.com>

From: Dean Rasheed <dean.a.rasheed@gmail.com>

To: Peter Eisentraut <peter@eisentraut.org>

Cc: pgsql-hackers <pgsql-hackers@postgresql.org>, jian he <jian.universality@gmail.com>

Date: 2025-01-13T18:15:15Z

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 →

Expand virtual generated columns for ALTER COLUMN TYPE
- 5069fef1cfae 18.0 landed
Eliminate code duplication in replace_rte_variables callbacks
- 363a6e8c6fcf 18.0 landed
Expand virtual generated columns in the planner
- 1e4351af329f 18.0 landed
Virtual generated columns
- 83ea6c54025b 18.0 landed
Additional tests for stored generated columns
- 41084409f635 18.0 landed
Improve generated_stored test
- 44b61efb7928 18.0 landed
- 86749ea3b766 18.0 landed
Fix handling of CREATE DOMAIN with GENERATED constraint syntax
- 84a67725cd11 18.0 landed
Add pg_constraint rows for not-null constraints
- 14e87ffa5c54 18.0 cited
Put generated_stored test objects in a schema
- 894be11adfa6 18.0 landed
Rename regress test generated to generated_stored
- b9ed4969250d 18.0 landed
Small code simplification
- 7ff9afbbd1df 18.0 landed
Remove useless code
- e26d313bad92 18.0 landed
Remove useless initializations
- da2aeba8f533 18.0 landed
doc: Clarify that pg_attrdef also stores generation expressions
- da486d360103 18.0 landed
Clean out column-level pg_init_privs entries when dropping tables.
- 76618097a6c0 17.0 cited
Re-implement the ereport() macro using __VA_ARGS__.
- e3a87b4991cc 13.0 cited

On Wed, 8 Jan 2025 at 16:14, Peter Eisentraut <peter@eisentraut.org> wrote:
>
> Here is a new patch version

In expand_generated_columns_in_expr():

+       RangeTblEntry *rte;
+
+       rte = makeNode(RangeTblEntry);
+       rte->relid = RelationGetRelid(rel);
+
+       node = expand_generated_columns_internal(node, rel, rt_index, rte);

This dummy RTE is a bit too minimal.

I think it should explicitly set rte->rtekind to RTE_RELATION, even
though that's technically not necessary since RTE_RELATION is zero.

In addition, it needs to set rte->eref, because expandRTE() (called
from ReplaceVarsFromTargetList()) needs that when expanding whole-row
variables. Here's a simple reproducer which crashes:

CREATE TABLE foo (a int, b int GENERATED ALWAYS AS (a*2) VIRTUAL);
ALTER TABLE foo ADD CONSTRAINT foo_check CHECK (foo IS NOT NULL);

Regards,
Dean