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Re: Re: SQL/JSON: functions

Andy Alsup <bluesbreaker@gmail.com>

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From: Andrew Alsup <bluesbreaker@gmail.com>
To: Nikita Glukhov <n.gluhov@postgrespro.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Andres Freund <andres@anarazel.de>, Dmitry Dolgov <9erthalion6@gmail.com>, Pavel Stehule <pavel.stehule@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: 2019-05-14T00:53:51Z
Lists: pgsql-hackers 
On 3/5/19 5:35 PM, Nikita Glukhov wrote:
> Attached 36th version of the patches rebased onto jsonpath v36.
While testing this patch a found a few issues:

[1] I was not able to apply the patch to the current HEAD. However, it 
applies cleanly to commit: e988878f85 (NOTE: I did not investigate which 
commit between e988878f85 and HEAD caused problems).

[2] JsonPath array slicing does not work. I'm not aware of a 
comprehensive list of JsonPath features/syntax that is targeted for 
support; however, I did try various forms of array slicing, which don't 
currently work.

Here are a few examples:

The input document is the same in each example.

{
   "a1": 123,
   "b1": "xxx",
   "c1": {
     "a2": 456,
     "b2": "yyy",
     "c2": [
       {"a3": 777, "b3": "7z"},
       {"a3": 888, "b3": "8z"}
     ]
   }
}

array wildcard selector [*] works: $.c1.c2[*].b3

# select json_path_query('{"a1": 123, "b1": "xxx", "c1": {"a2": 456, 
"b2": "yyy", "c2": [{"a3": 777, "b3": "7z"},{"a3": 888, "b3": 
"8z"}]}}'::json, '$.c1.c2[*].b3'::jsonpath);
  json_path_query
-----------------
  "7z"
  "8z"
(2 rows)

array index selector [0] works: $.c1.c2[0].b3

jsonpatch=# select json_path_query('{"a1": 123, "b1": "xxx", "c1": 
{"a2": 456, "b2": "yyy", "c2": [{"a3": 777, "b3": "7z"},{"a3": 888, 
"b3": "8z"}]}}'::json, '$.c1.c2[0].b3'::jsonpath);
  json_path_query
-----------------
  "7z"
(1 row)

array slicing [0:], [:1], and [0:1] do not work:$.c1.c2[0:].b3

# select json_path_query('{"a1": 123, "b1": "xxx", "c1": {"a2": 456, 
"b2": "yyy", "c2": [{"a3": 777, "b3": "7z"},{"a3": 888, "b3": 
"8z"}]}}'::json, '$.c1.c2[0:].b3'::jsonpath);
2019-05-13 20:47:48.740 EDT [21856] ERROR:  bad jsonpath representation 
at character 147
2019-05-13 20:47:48.740 EDT [21856] DETAIL:  syntax error, unexpected 
':', expecting ',' or ']' at or near ":"
2019-05-13 20:47:48.740 EDT [21856] STATEMENT:  select 
json_path_query('{"a1": 123, "b1": "xxx", "c1": {"a2": 456, "b2": "yyy", 
"c2": [{"a3": 777, "b3": "7z"},{"a3": 888, "b3": "8z"}]}}'::json, 
'$.c1.c2[0:].b3'::jsonpath);
ERROR:  bad jsonpath representation
LINE 1: ...7, "b3": "7z"},{"a3": 888, "b3": "8z"}]}}'::json, '$.c1.c2[0...
                                                              ^
DETAIL:  syntax error, unexpected ':', expecting ',' or ']' at or near ":"

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.