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From: jian he <jian.universality@gmail.com>
Date: Thu, 7 Nov 2024 15:10:33 +0800
Message-ID: <CACJufxEYG7qD9t=qq=28ZLagA43dSE5c1FD7me+cto7QxZNcuQ@mail.gmail.com>
Subject: Re: not null constraints, again
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>, Tender Wang <tndrwang@gmail.com>
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RemoveInheritance
            if (copy_con->coninhcount <= 0) /* shouldn't happen */
                elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
                     RelationGetRelid(child_rel), NameStr(copy_con->conname));
dropconstraint_internal
        if (childcon->coninhcount <= 0) /* shouldn't happen */
            elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
                 childrelid, NameStr(childcon->conname));

RemoveInheritance error triggered (see below), dropconstraint_internal may also.
that means the error message should use RelationGetRelationName
rather than plain "relation %u"?


drop table if exists inh_parent,inh_child1,inh_child2;
create table inh_parent(f1 int not null no inherit);
create table inh_child1(f1 int not null no inherit);
alter table inh_child1 inherit inh_parent;
alter table inh_child1 NO INHERIT inh_parent;
ERROR:  relation 26387 has non-inherited constraint "inh_child1_f1_not_null"

sql-altertable.html
INHERIT parent_table
        This form adds the target table as a new child of the
specified parent table.
        Subsequently, queries against the parent will include records
of the target
        table.  To be added as a child, the target table must already
contain all the
        same columns as the parent (it could have additional columns,
too).  The columns
        must have matching data types, and if they have NOT NULL
constraints in the
        parent then they must also have NOT NULL constraints in the child.

"
The columns must have matching data types, and if they have NOT NULL
constraints in the
 parent then they must also have NOT NULL constraints in the child.
"
For the above sentence, we need to add some text to explain
NOT NULL constraints, NO INHERIT property
for the child table and parent table.

------------------------------------------------
drop table if exists inh_parent,inh_child1,inh_child2;
create table inh_parent(f1 int not null no inherit);
create table inh_child1(f1 int);
alter table inh_child1 inherit inh_parent;
alter table inh_child1 NO INHERIT inh_parent;
ERROR:  1 unmatched constraints while removing inheritance from
"inh_child1" to "inh_parent"

now, we cannot "uninherit" inh_child1 from inh_parent?
not sure this is expected behavior.