When using multiple inheritance, insufficient tests exist for whether a data type change is safe.

Minimal reproduceable example:

create table buggy (Id int);
create table buggy2 (like buggy) inherits (buggy);
create table buggy3 (like buggy);
alter table buggy2 inherit buggy3;
alter table buggy3 alter id type bigint;
insert into buggy2 (Id) values (3000000000);
select * from buggy;

Result:

ERROR: attribute "id" of relation "buggy2" does not match parent's type

Now note that when adding an inheriting table this is checked.

bug=# alter table buggy2 inherit buggy4;

ERROR: child table "buggy2" has different type for column "id"

However this allows types to propagate in inconsistent ways down an
inheritance tree with multiple inheritance and could bring queries to a
screeching halt.....

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Best Regards,
Chris Travers
Database Administrator

Tel: +49 162 9037 210 | Skype: einhverfr | www.adjust.com
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