On 6/15/16, Tom Lane <t...@sss.pgh.pa.us> wrote: > Michael Paquier <michael.paqu...@gmail.com> writes: >> To put it short, it should not be possible to drop a NOT NULL >> constraint on a child relation when its parent table is using it, this >> should only be possible from the parent. Attached is a patch handling >> this problem by adding a new function in pg_inherits.c to fetch the >> list of parent relations for a given relation OID, and did some >> refactoring to stick with what is done when scanning child relations. > > This doesn't sound like the right approach; in particular, it won't really > help for deciding whether to propagate a DROP NOT NULL on a parent rel to > its children. What we've discussed in the past is to store NOT NULL > constraints in pg_constraint, much like CHECK constraints are already, and > use use-count logic identical to the CHECK case to keep track of whether > NOT NULL constraints are inherited or not. My feeling is that we'd keep > the pg_attribute.attnotnull field and continue to drive actual enforcement > off that, but it would just reflect a summary of the pg_constraint state. > > IIRC, Alvaro posted a WIP patch for that awhile back. Not sure what the > current state is. > > regards, tom lane
The last thread about NOT NULLs as constraints is accessible by the link[1]. I rebased[2] Alvaro's patch to the actual master at that time, but I have not repeated it since then. In the initial letter[1] I posted a digest from the SQL-2011 standard and a conclusion as a design of a new patch. Now I have more free time and I'm hacking it that way. The new patch is at the very early stage, full of WIPs and TODOs. I hope it'll be ready to be shown in a month (may be two). But it already forbids dropping NOT NULLs if they were set as result of inheritance. [1] https://www.postgresql.org/message-id/flat/CAKOSWNkN6HSyatuys8xZxzRCR-KL1OkHS5-b9qd9bf1Rad3PLA%40mail.gmail.com [2] https://www.postgresql.org/message-id/attachment/41886/catalog-notnull-2-c477e84_cleaned.patch -- Best regards, Vitaly Burovoy -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
