Only flatten array/object for relational DBs

lib/dao.js

@@ -40,6 +40,9 @@ function DataAccessObject() {
 
 
 DataAccessObject._forDB = function (data) {
+    if(!this.schema.isRelational()) {
+        return data;
+    }
     var res = {};
     Object.keys(data).forEach(function (propName) {
         if (this.whatTypeName(propName) === 'JSON' || data[propName] instanceof Array) {

lib/datasource.js

@@ -1271,6 +1271,10 @@ DataSource.prototype.defineOperation = function (name, options, fn) {
   this._operations[name] = options;
 }
 
+DataSource.prototype.isRational = function() {
+    return this.adapter && this.adapter.relational;
+}
+
 /**
  * Define hidden property
  */

lib/sql.js

@@ -6,6 +6,8 @@ module.exports = BaseSQL;
 function BaseSQL() {
 }
 
+BaseSQL.prototype.rational = true;
+
 BaseSQL.prototype.query = function () {
     throw new Error('query method should be declared in adapter');
 };