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Posted to issues@calcite.apache.org by "xuqianjin (JIRA)" <ji...@apache.org> on 2019/01/26 11:07:00 UTC

[jira] [Created] (CALCITE-2810) Add the JSON_LENGTH function

xuqianjin created CALCITE-2810:
----------------------------------

             Summary: Add the JSON_LENGTH function
                 Key: CALCITE-2810
                 URL: https://issues.apache.org/jira/browse/CALCITE-2810
             Project: Calcite
          Issue Type: Improvement
            Reporter: xuqianjin
            Assignee: Julian Hyde


{{JSON_LENGTH(*json_doc*[, *path*\])}}

Returns the length of a JSON document, or, if a _path_ argument is given, the length of the value within the document identified by the path. Returns {{NULL}} if any argument is {{NULL}} or the _path_ argument does not identify a value in the document. An error occurs if the _json_doc_ argument is not a valid JSON document or the _path_ argument is not a valid path expression or contains a {{*}} or {{**}} wildcard.

The length of a document is determined as follows:
 * The length of a scalar is 1.

 * The length of an array is the number of array elements.

 * The length of an object is the number of object members.

 * The length does not count the length of nested arrays or objects.

SELECT JSON_LENGTH('[1, 2, \{"a": 3}]');
+---------------------------------+
| JSON_LENGTH('[1, 2, \{"a": 3}]') |
+---------------------------------+
|                               3 |
+---------------------------------+
SELECT JSON_LENGTH('\{"a": 1, "b": {"c": 30}}');
+-----------------------------------------+
| JSON_LENGTH('\{"a": 1, "b": {"c": 30}}') |
+-----------------------------------------+
|                                       2 |
+-----------------------------------------+
SELECT JSON_LENGTH('\{"a": 1, "b": {"c": 30}}', '$.b');
+------------------------------------------------+
| JSON_LENGTH('\{"a": 1, "b": {"c": 30}}', '$.b') |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+



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