gem-hunter

postgres-json-schema allows validation of JSON schemas in PostgreSQL. It is implemented as a PL/pgSQL function and you can use it as a check constraint to validate the format of your JSON columns.

postgres-json-schema supports the entire JSON schema draft v4 spec, except for remote (http) references. It's tested against the official JSON-Schema-Test-Suite.

postgres-json-schema is packaged as an PGXS extension. To install, just run make install as root, then CREATE EXTENSION "postgres-json-schema"; as the database superuser.

CREATE TABLE example (id serial PRIMARY KEY, data jsonb);
ALTER TABLE example ADD CONSTRAINT data_is_valid CHECK (validate_json_schema('{"type": "object"}', data));

INSERT INTO example (data) VALUES ('{}');
-- INSERT 0 1

INSERT INTO example (data) VALUES ('1');
-- ERROR:  new row for relation "example" violates check constraint "data_is_valid"
-- DETAIL:  Failing row contains (2, 1).