[CASSANDRA-7970] JSON support for CQL

• Type: New Feature
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 2.2.0 beta 1
• Component/s: Legacy/CQL
• Labels: cql3.3
• Impacts: Docs
• Assignee: Tom Hobbs
• Reporter: Jonathan Ellis

Authors

Tom Hobbs

Reviewers

Sylvain Lebresne

• Created: 18/Sep/14 16:53
• Updated: 06/Nov/19 22:05
• Resolved: 01/Apr/15 17:44

Description

JSON is popular enough that not supporting it is becoming a competitive weakness. We can add JSON support in a way that is compatible with our performance goals by mapping JSON to an existing schema: one JSON documents maps to one CQL row.

Thus, it is NOT a goal to support schemaless documents, which is a misfeature [1] [2] [3]. Rather, it is to allow a convenient way to easily turn a JSON document from a service or a user into a CQL row, with all the validation that entails.

Since we are not looking to support schemaless documents, we will not be adding a JSON data type (CASSANDRA-6833) a la postgresql. Rather, we will map the JSON to UDT, collections, and primitive CQL types.

Here's how this might look:

CREATE TYPE address (
  street text,
  city text,
  zip_code int,
  phones set<text>
);

CREATE TABLE users (
  id uuid PRIMARY KEY,
  name text,
  addresses map<text, address>
);

INSERT INTO users JSON
{‘id’: 4b856557-7153,
   ‘name’: ‘jbellis’,
   ‘address’: {“home”: {“street”: “123 Cassandra Dr”,
                        “city”: “Austin”,
                        “zip_code”: 78747,
                        “phones”: [2101234567]}}};

SELECT JSON id, address FROM users;

(We would also want to_json and from_json functions to allow mapping a single column's worth of data. These would not require extra syntax.)

[1] http://rustyrazorblade.com/2014/07/the-myth-of-schema-less/
[2] https://blog.compose.io/schema-less-is-usually-a-lie/
[3] http://dl.acm.org/citation.cfm?id=2481247

Issue Links

• is depended upon by: CASSANDRA-8837 Support toJson() and fromJson() in all contexts