On Wed, 6 Mar 2019 at 08:41, Sergei Kornilov <s...@zsrv.org> wrote: > In this case we need extra argument for ConstraintImpliedByRelConstraint for > some caller-provided existConstraint, right? Along with Relation itself? Then > I need make copy of existConstraint, append relation constraints and call > predicate_implied_by. If I understood correctly pseudocode would be: > > PartConstraintImpliedByRelConstraint(rel, testConstraint) > generate notNullConstraint from NOT NULL table attributes > call ConstraintImpliedByRelConstraint(rel, testConstraint, > notNullConstraint) > > ConstraintImpliedByRelConstraint(rel, testConstraint, existsConstraint) > copy existsConstraint to localExistsConstraint variable > append relation constraints to localExistsConstraint list > call predicate_implied_by > > I thing redundant IS NOT NULL check is not issue here and we not need extra > arguments for ConstraintImpliedByRelConstraint. Was not changed in attached > version, but I will change if you think this would be better design.
I was really just throwing the idea out there for review. I don't think that I'm insisting on it. FWIW I think you could get away without the copy of the constraint providing it was documented that the list is modified during the ConstraintImpliedByRelConstraint call and callers must make a copy themselves if they need an unmodified version. Certainly, PartConstraintImpliedByRelConstraint won't need to make a copy, so there's probably not much reason to assume that possible future callers will. Providing I'm imagining it correctly, I do think the patch is slightly cleaner with that change. It's: a) slightly more efficient due to not needlessly checking a bunch of IS NOT NULLs (imagine a 1000 column table with almost all NOT NULL and a single CHECK constraint); and b) patch has a smaller footprint (does not modify existing callers of PartConstraintImpliedByRelConstraint()); and c) does not modify an existing API function. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
