Re: [PATCH] Generic type subscripting

On Mon, Sep 18, 2017 at 10:31:54AM +0200, Dmitry Dolgov wrote:
> Just to clarify, do you mean that `CREATE SUBSCRIPTING FOR` would only make
> a
> dependency record? In this case `DROP SUBSCRIPTING FOR` actually means just
> drop an init function.

I think it would be good to add new catalog table. It may be named as pg_type_sbs or pg_subscripting (second is better I think).
This table may have the fields:
- oid
- sbstype
- sbsinit
- sbsfetch
- sbsassign

And command 'CREATE SUBSCRIPTING' should add an entry to the pg_subscripting table. It also adds entries to the pg_depend table: dependency between pg_type and pg_subscripting, dependency between pg_type and pg_proc.
'DROP SUBSCRIPTING' should drop this entries, it should not drop init function.

According to the Tom's comment the syntax can be modified in the following way:

CREATE SUBSCRIPTING FOR type_namei (
INITFUNC = subscripting_init_func
FETCHFUNC = subscripting_fetch_func
ASSIGNFUNC = subscripting_assign_func
)
DROP SUBSCRIPTING FOR type_name

--
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company