Tender, sorry, you patch is perfect. I badly tested it this morning. My fault. There is just the case with the constant that is not handled (select * from a left join (select 1 const1 from b) x where x.const1 is null) but i don't think it worth handling it. I added 2 regresssion tests in case you want to add them to your patch. The first one is important, the second one is just to confirm that subqueries are working. I've added 3 new tables because in test_setup.sql and join.sql there were no table with not null constraints.
Again, thanks a lot.
Thanks for your provided test cases. I had added it to the v3 patch.
