Hi, all
I haven't paid attention to this topic in a long time, thanks all for the advices, I will study them then update. Thanks again. Zhang Mingli www.hashdata.xyz On Sep 18, 2024 at 15:50 +0800, David Rowley <dgrowle...@gmail.com>, wrote: > On Wed, 18 Sept 2024 at 19:28, Peter Eisentraut <pe...@eisentraut.org> wrote: > > > > On 12.09.24 03:43, David Rowley wrote: > > > (Likely it could just look at pg_attribute.attnotnull instead) > > > > That won't work because you can't record dependencies on that. (This is > > one of the reasons for cataloging not-null constraints as real constraints.) > > I'm not seeing any need to record constraint dependencies for this > optimisation. It would be different for detecting functional > dependencies in a view using a unique constraint+not null constraints > for ungrouped columns, but that's not what this is. This is just a > planner optimisation. The plan can be invalidated by a relcache > invalidation, which will happen if someone does ALTER TABLE DROP NOT > NULL. > > For reference, see 5b736e9cf. > > David
