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Tyler Hobbs commented on CASSANDRA-7970:
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[~lhartzman] that's a fair point. We had similar debates about supporting
other (Cassandra) types that JSON doesn't support natively, like UUIDs. The
decision was that if we didn't support those types, users would end up using
strings instead. The downside to this is a lack of type safety, validation,
and correct sorting. Additionally, functions become incompatible and drivers
(including cqlsh) no longer have proper type information.
I think the same argument can be applied here. Users will want to use maps
keyed by ints, uuids, frozen sets, etc. If we don't support that, they'll
simply declare the keys to be strings instead, and the same problems around
losing type information will come up.
> JSON support for CQL
> --------------------
>
> Key: CASSANDRA-7970
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7970
> Project: Cassandra
> Issue Type: New Feature
> Components: API
> Reporter: Jonathan Ellis
> Assignee: Tyler Hobbs
> Fix For: 3.0
>
>
> 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:
> {code}
> 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;
> {code}
> (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
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