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Re: SQL/JSON: functions

Pavel Stehule <pavel.stehule@gmail.com>

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From: Pavel Stehule <pavel.stehule@gmail.com>
To: Nikita Glukhov <n.gluhov@postgrespro.ru>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, Erik Rijkers <er@xs4all.nl>, Alvaro Herrera <alvherre@2ndquadrant.com>, Thomas Munro <thomas.munro@gmail.com>, Andrew Alsup <bluesbreaker@gmail.com>, Andres Freund <andres@anarazel.de>, Dmitry Dolgov <9erthalion6@gmail.com>, Oleg Bartunov <obartunov@postgrespro.ru>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Michael Paquier <michael@paquier.xyz>, Simon Riggs <simon@2ndquadrant.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Date: 2020-03-17T18:35:00Z
Lists: pgsql-hackers 
út 17. 3. 2020 v 1:55 odesílatel Nikita Glukhov <n.gluhov@postgrespro.ru>
napsal:

> Attached 44th version of the patches.
>
>
> On 12.03.2020 16:41, Pavel Stehule wrote:
>
>
> On 12.03.2020 00:09 Nikita Glukhov wrote:
>
>> Attached 43rd version of the patches.
>>
>> The previous patch #4 ("Add function formats") was removed.
>> Instead, introduced new executor node JsonCtorExpr which is used to wrap
>> SQL/JSON constructor function calls (FuncExpr, Aggref, WindowFunc).
>>
>> Also, JsonIsPredicate node began to be used as executor node.
>> This helped to remove unnecessary json[b]_is_valid() user functions.
>>
>>
> It looks very well - all tests passed, code looks well.
>
> Now, when there are special nodes, then the introduction of
> COERCE_INTERNAL_CAST is not necessary, and it is only my one and last
> objection again this patch's set.
>
> I have removed patch #3 with COERCE_INTERNAL_CAST too.
>
> Coercions in JsonValueExpr in JsonCtorExpr, which were previously hidden with
> COERCE_INTERNAL_CAST and which were outputted as RETURNING or FORMAT JSON
> clauses, now moved into separate expressions.
>
> I am looking on the code, and although the code is correct it doesn't look
well (consistently with other node types).

I think so JsonFormat and JsonReturning should be node types, not just
structs. If these types will be nodes, then you can simplify _readJsonExpr
and all node operations on this node.


>
>
> User functions json[b]_build_object_ext() and json[b]_build_array_ext() also
> can be easily removed.   But it seems harder to remove new aggregate functions
> json[b]_objectagg() and json[b]_agg_strict(), because they can't be called
> directly from JsonCtorExpr node.
>
>
I don't see reasons for another reduction now. Can be great if you can
finalize work what you plan for pg13.

+<->READ_ENUM_FIELD(on_error.btype, JsonBehaviorType);
+<->READ_NODE_FIELD(on_error.default_expr);
+<->READ_ENUM_FIELD(on_empty.btype, JsonBehaviorType);
+<->READ_NODE_FIELD(on_empty.default_expr);

JsonBehavior is node type. Then why you don't write just

READ_NODE_FIELD(on_error);
READ_NODE_FIELD(on_empty)

??

And maybe the code can be better if you don't use JsonPassing struct (or
use it only inside gram.y) and pass just List *names, List *values.

Nodes should to contains another nodes or scalar types. Using structs (that
are not nodes)  inside doesn't look consistently.



I found some not finished code in 0003 patch
+
+json_name_and_value:
+/* TODO
+<-><--><-->KEY c_expr VALUE_P json_value_expr %prec POSTFIXOP
+<-><--><--><-->{ $$ = makeJsonKeyValue($2, $4); }
+<-><--><-->|
+*/



> The support for json type in jsonpath also seems to be immature, so I will try
> to remove it in the next iteration.
>
> What do you think? This patch is little bit off topic, so if you don't
need it, then can be removed. Is there some dependency for "jsontable" ?

Regards

Pavel





> --
> Nikita Glukhov
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
>
>

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. JSON_TABLE: Add support for NESTED paths and columns

  2. Add basic JSON_TABLE() functionality

  3. Add SQL/JSON query functions

  4. Add soft error handling to some expression nodes

  5. Adjust populate_record_field() to handle errors softly

  6. Refactor code used by jsonpath executor to fetch variables

  7. Add more SQL/JSON constructor functions

  8. SQL/JSON: support the IS JSON predicate

  9. SQL/JSON: add standard JSON constructor functions

  10. Improve readability of SQL/JSON documentation.

  11. Documentation for SQL/JSON features

  12. RETURNING clause for JSON() and JSON_SCALAR()

  13. SQL JSON functions

  14. SQL/JSON query functions

  15. IS JSON predicate

  16. SQL/JSON constructors

  17. Common SQL/JSON clauses

  18. Doc: remove obsolete entries in table of BRIN strategy numbers.

  19. Doc: standardize markup a bit more.

  20. Make pg_regress.c unset PGDATABASE during make installcheck.

  21. Fix handling of GENERATED columns in CREATE TABLE LIKE INCLUDING DEFAULTS.