Horton

Re: Virtual generated columns

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Alexander Lakhin <exclusion@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: 2025-05-16T07:26:01Z
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__.

On Fri, May 16, 2025 at 1:00 PM Alexander Lakhin <exclusion@gmail.com> wrote:
> 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

Thank you for the report.  It seems that we fail to expand references
to virtual generated columns in the NewColumnValues expression when
altering tables.  We might be able to fix it by:

@@ -6203,7 +6203,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
        NewColumnValue *ex = lfirst(l);

        /* expr already planned */
-       ex->exprstate = ExecInitExpr((Expr *) ex->expr, NULL);
+       ex->exprstate = ExecInitExpr((Expr *)
expand_generated_columns_in_expr((Node *) ex->expr, oldrel, 1), NULL);

Thanks
Richard