Subject: Re: Re: SQL/JSON: functions
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>
References: 
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 <6862ba8f-70bf-6dd8-5651-5d9050c8f4de@postgrespro.ru>
 <e467c355-6fc7-e1b0-44d5-9707eca8f1dd@postgrespro.ru>
 <CAFj8pRCQdkhzNj+hK37hiTcbCrCikPri4DutuYi2Tan-5nCiVg@mail.gmail.com>
 <fa8da193-52d8-adc9-2422-753f8b53bff8@postgrespro.ru>
 <CAFj8pRA8620MsUBN3tvoqJT00n7rZpYRSG5r_wfLWK9WZnvuyw@mail.gmail.com>
 <CA+q6zcWRdZhdT2ZJxCbfHJY=9KmXoye5msCXySeWCRPp5R-o_w@mail.gmail.com>
 <bd364cce-2624-2ad3-1744-74a583ea6625@postgrespro.ru>
 <CA+q6zcU=kiYPPcNK7EOuM08FDBNjco0U+=so1LwgfSKuCRsJ5Q@mail.gmail.com>
 <579f9020-7844-617c-20db-a04e87125983@postgrespro.ru>
 <20190216051239.wvhizo3hg2lwqyzh@alap3.anarazel.de>
 <70d2bf4f-f932-15f3-4037-90acce48a3b6@postgrespro.ru>
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From: Andrew Alsup <bluesbreaker@gmail.com>
Message-ID: <bf877956-997d-9392-74ac-539f17ed72e0@gmail.com>
Date: Mon, 13 May 2019 20:53:51 -0400
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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 ":"