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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: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-09-20T08:12:28Z
Lists: pgsql-hackers 
On Tue, Sep 19, 2017 at 09:01:57PM -0400, Peter Eisentraut wrote:
> Would you mind posting a summary of how you go here?

There were several points here to me:
- it is necessary to solve the dependency problem (it can be solved also by adding several oid fields to the pg_type)
- users may want to add subscripting to their existing type, which already created in their database, or drop subscripting from existing type (it cannot be done by CREATE TYPE)
- other type related functionalities have their CREATE command and system catalog table. For example, CREATE CAST, CREATE TRANSFORM (this is a weakest point I think, mostly because of several casts and transforms can be defined to one type, and only one subscripting can be defined to one type).

> Superficially, it seems like this sort of feature should be handled by a
> couple of type attributes and pg_type columns.  But you are talking
> about a new system catalog and new DDL, and it's not clear to me how you
> got here.
> 
> -- 
> Peter Eisentraut              http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

You are right of course. It can be handled by oid columns of *_parse, *_extract and *_assign functions. Also it is clear to me now that the second point can be handled by ALTER TYPE command. The command should be modified to handle it of course. And it can be modified by a separate patch later.

I want to emphasize that I don't insist on CREATE SUBSCRIPTING command. The patch brings important functionality and I don't want to be a person who blocked it from commiting.

-- 
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.