xuqianjin created CALCITE-2808:
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Summary: Add the JSON_LENGTH function
Key: CALCITE-2808
URL: https://issues.apache.org/jira/browse/CALCITE-2808
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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