Re: Re: SQL/JSON: functions

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 ":"