Horton

Re: [HACKERS] [PATCH] Generic type subscripting

Pavel Stehule <pavel.stehule@gmail.com>

View thread View on postgr.es
From: Pavel Stehule <pavel.stehule@gmail.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Oleksandr Shulgin <oleksandr.shulgin@zalando.de>, Artur Zakirov <a.zakirov@postgrespro.ru>, Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael.paquier@gmail.com>, Oleg Bartunov <obartunov@gmail.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, David Steele <david@pgmasters.net>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2018-10-10T12:25:33Z
Lists: pgsql-hackers 
Hi

ne 30. 9. 2018 v 8:23 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
napsal:

>
>
> ne 30. 9. 2018 v 0:21 odesílatel Dmitry Dolgov <9erthalion6@gmail.com>
> napsal:
>
>> > On Fri, 20 Jul 2018 at 23:32, Dmitry Dolgov <9erthalion6@gmail.com>
>> wrote:
>> >
>> > > On Thu, 26 Apr 2018 at 16:44, Dmitry Dolgov <9erthalion6@gmail.com>
>> wrote:
>> > >
>> > > > On 22 March 2018 at 23:25, Dmitry Dolgov <9erthalion6@gmail.com>
>> wrote:
>> > > >
>> > > > Here is the updated version of patch, rebased after recent
>> conflicts and with
>> > > > suggested documentation improvements.
>> > >
>> > > Another rebased version of the patch.
>> >
>> > I've noticed, that I never updated llvmjit code for the arrayref
>> expressions,
>> > and it's important to do so, since the patch introduces another layer of
>> > flexibility. Hence here is the new version.
>>
>> Here is another rebased version, and a bit of history: the first
>> prototypes of
>> this patch were sent more than 3 years ago. Of course the patch evolved
>> significantly over this period, and I take it as a good sign that it
>> wasn't
>> rejected and keeps moving through the commitfests. At the same time the
>> lack of
>> attention makes things a bit frustrating. I have an impression that it's
>> sort
>> of regular situation and wonder if there are any ideas (besides the well
>> known
>> advice of putting some efforts into review patches from other people,
>> since I'm
>> already doing my best and enjoying this) how to make progress in such
>> cases?
>>
>
> This feature looks nice, and it can be great when some values of some not
> atomic type should be updated.
>

I am playing with this feature little bit

I have one idea - can be possible to use integer subscript for record
fields? It can helps with iteration over record.

example:

select ('{"a":{"a":[10,20]}}'::jsonb)[0];--> NULL, but can be more
practical if it returns same like select
('{"a":{"a":[10,"20"]}}'::jsonb)['a'];

I don't like quite ignoring bad subsript in update

postgres=# insert into test(v) values( '[]');
INSERT 0 1
postgres=# update test set v[1000] = 'a';
UPDATE 1
postgres=# update test set v[1000] = 'a';
UPDATE 1
postgres=# update test set v[1000] = 'a';
UPDATE 1
postgres=# select * from test;
┌────┬─────────────────┐
│ id │        v        │
╞════╪═════════════════╡
│    │ ["a", "a", "a"] │
└────┴─────────────────┘
(1 row)

It should to raise exception in this case. Current behave allows append
simply, but can be source of errors. For this case we can introduce some
special symbol - some like -0 :)

It is maybe strange, but I prefer less magic syntax like

update test set v['a']['a'] =  v['a']['a'] || '1000';

more readable than

update test set v['a']['a'][1000000] = 1000;

My first impression is very good - update jsonb, xml documents can be very
friendly.

Regards

Pavel






>
> Regards
>
> Pavel
>

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.