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Posted to commits@cassandra.apache.org by "Tyler Hobbs (JIRA)" <ji...@apache.org> on 2014/11/06 22:37:36 UTC
[jira] [Commented] (CASSANDRA-7970) JSON support for CQL
[ https://issues.apache.org/jira/browse/CASSANDRA-7970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14200974#comment-14200974 ]
Tyler Hobbs commented on CASSANDRA-7970:
----------------------------------------
There's one problem that I forgot about: the JSON spec only accepts strings for map keys.
I think that leaves us with two options:
# Accept a string version of anything (including ints, floats, etc). For example, if we're expecting a float when decoding JSON and the JSON decoder returns a String, we should try to create a float from it. For {{toJson()}}, we would convert non-strings to strings when they're map keys.
# Don't allow {{toJson()}} and {{fromJson()}} to be used on maps with non-string keys. If we have transform functions at some point, those could be used to support these kinds of maps.
Option 2 would be my preference.
> JSON support for CQL
> --------------------
>
> Key: CASSANDRA-7970
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7970
> Project: Cassandra
> Issue Type: Bug
> 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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