[HACKERS] deficiency on delete and update instead rules for views

[Zeugswetter Andreas SB]

We lack a syntax that would enable us to write an on update/delete do instead rule
that would efficiently map an update/delete to a table that is referenced by a view.

Currently the only rule you can implement is one that uses a primary key.
This has the disadvantage of needing a self join to find the appropriate rows.

Andreas