Re: Updating system catalogs after a tuple deletion

At 23:34 14/05/01 -0400, Tom Lane wrote:
>Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
>> It is worth considering skipping the entire 'copy to children' approach?
>> Something like:
>> pg_constraints(constraint_id, constraint_name, constraint_details....)
>> pg_relation_constraints(rel_id, constraint_id)
>> Then, when we drop constraint 'FRED', the relevant rows of these tables are
>> deleted. There is only ever one copy of the constraint definition.
...
>
>A small advantage of doing it this way is that it'd be easier to detect
>the case where the same constraint is multiply inherited from more than
>one parent, as in
>

Other advantages include:

- easy ALTER TABLE ALTER CONSTRAINT (does it exist?)
- cleaner pg_dump code
- possibility to have NULL names for system objects which avoids any
namespace corruption.

It's probably worth adding extra information to the pg_constraints table to
include inform,ation about how it was created (pk, fk, user-defined etc).

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