text: CREATE SEQUENCE schema_versions_id_seq;
  CREATE TABLE schema_versions (
    id BIGINT PRIMARY KEY DEFAULT nextval('schema_versions_id_seq'::regclass),
    version INTEGER DEFAULT 1,
    subject_id BIGINT NOT NULL,
    schema_id BIGINT NOT NULL
  );
  
  CREATE UNIQUE INDEX index_schema_versions_on_subject_id_and_version ON schema_versions(subject_id, version);
  