On Thu, Apr 3, 2025 at 8:33 PM Peter Eisentraut <pe...@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
