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We support changing NO INHERIT constraint to INHERIT for constraints in child relations when adding a constraint to some ancestor relation, and also during pg_upgrade's schema restore; but other than those special cases, command ALTER TABLE ADD CONSTRAINT should not be allowed to change an existing constraint from NO INHERIT to INHERIT, as that would require to process child relations so that they also acquire an appropriate constraint, which we may not be in a position to do. (It'd also be surprising behavior.) It is conceivable that we want to allow ALTER TABLE SET NOT NULL to make such a change; but in that case some more code is needed to implement it correctly, so for now I've made that throw the same error message. Also, during the prep phase of ALTER TABLE ADD CONSTRAINT, acquire locks on all descendant tables; otherwise we might operate on child tables on which no locks are held, particularly in the mode where a primary key causes not-null constraints to be created on children. Reported-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/7d923a66-55f0-3395-cd40-81c142b5448b@gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
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