Horton

Re: [PATCH] Generic type subscripting

Artur Zakirov <a.zakirov@postgrespro.ru>

View thread View on postgr.es
From: Arthur Zakirov <a.zakirov@postgrespro.ru>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-09-18T09:39:44Z
Lists: pgsql-hackers 
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

Commits

  1. Throw error when assigning jsonb scalar instead of a composite object

  2. Filling array gaps during jsonb subscripting

  3. Implementation of subscripting for jsonb

  4. Allow ALTER TYPE to update an existing type's typsubscript value.

  5. Allow subscripting of hstore values.

  6. Support subscripting of arbitrary types, not only arrays.

  7. jit: Reference function pointer types via llvmjit_types.c.

  8. Teach contain_leaked_vars that assignment SubscriptingRefs are leaky.

  9. jit: Correct parameter type for generated expression evaluation functions.

  10. Renaming for new subscripting mechanism

  11. Fix assertion failure for SSL connections.

  12. Teach eval_const_expressions() to handle some more cases.