Re: Virtual generated columns

On Thu, 8 Aug 2024 at 07:23, Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:
>
> Thank you for your extensive testing. Here is a new patch set that has
> fixed all the issues you have reported (MERGE, sublinks, statistics,
> ANALYZE).

I had a quick look at this and found one issue, which is that it
doesn't properly deal with virtual generated columns in wholerow
attributes:

CREATE TABLE foo(a int, a2 int GENERATED ALWAYS AS (a*2) VIRTUAL);
INSERT INTO foo VALUES (1);
SELECT foo FROM foo;

foo
------
(1,)
(1 row)

Looking at the rewriter changes, it occurred to me that it could
perhaps be done more simply using ReplaceVarsFromTargetList() for each
RTE with virtual generated columns. That function already has the
required wholerow handling code, so there'd be less code duplication.
I think it might be better to do this from within fireRIRrules(), just
after RLS policies are applied, so it wouldn't need to worry about
CTEs and sublink subqueries. That would also make the
hasGeneratedVirtual flags unnecessary, since we'd already only be
doing the extra work for tables with virtual generated columns. That
would eliminate possible bugs caused by failing to set those flags.

Regards,
Dean