Re: Support NOT VALID / VALIDATE constraint options for named NOT NULL constraints

On Thu, Apr 3, 2025 at 8:33 PM Peter Eisentraut <peter@eisentraut.org>
wrote:

> On 03.04.25 10:07, Alvaro Herrera wrote:
> > The new flag is there for quick access by get_relation_info.  We could
> > easily not have it otherwise, because clients don't need it, but its
> > lack would probably make planning measurably slower because it'd have to
> > do syscache access for every single not-null constraint to figure out if
> > it's valid or not.
>
> In the v6 patch, you are adding a attnullability field to the
> CompactAttribute in the tuple descriptor and use that in
> get_relation_info().  That seems like the right approach, because then
> you're doing all that preprocessing about which constraint is active in
> the relcache.  So I don't see where the extra pg_attribute field
> attnotnullvalid is getting used.'
>

attnotnullvalid is getting used to populate the CompatAttribute
(populate_compact_attribute_internal).
The primary reason for adding a new field to pg_attribute is to avoid the
need for an additional scan
of pg_constraint when populating CompatAttribute, as this extra scan
introduces performance overhead
while retrieving catalog information for a relation.



-- 
Rushabh Lathia