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Re: [PATCH] Generic type subscripting

Artur Zakirov <a.zakirov@postgrespro.ru>

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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: 2017-09-19T08:21:43Z
Lists: pgsql-hackers 
On Mon, Sep 18, 2017 at 12:25:04PM +0200, Dmitry Dolgov wrote:
> > 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
> 
> What is `sbstype`?

'sbstype' is oid of type from pg_type for which subscripting is created. I.e. pg_type may not have the 'typsubsparse' field.

> > 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.
> 
> Why we should keep those subscripting functions? From my understanding
> they're
> totally internal and useless without subscripting context.
> 

Other similar commands do not drop related functions. For example 'DROP CAST' do not drop a function used to perform a cast.

> It also adds entries to the pg_depend table: dependency between pg_type and pg_subscripting, dependency between pg_type and pg_proc.

Here was a typo from me. Last entry is dependency between pg_subscripting and pg_proc.

-- 
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.