* Insert or update a single row. An update will be executed if a row which matches the supplied values on either the primary key or a unique key is found. Note that the unique index must be defined in your sequelize model and not just in the table. Otherwise you may experience a unique constraint violation, because sequelize fails to identify the row that should be updated.
*
* **Implementation details:**
*
* * MySQL - Implemented as a single query `INSERT values ON DUPLICATE KEY UPDATE values`
* * PostgreSQL - Implemented as two queries `WITH upsert AS (update_query) insert_query WHERE NOT EXISTS (SELECT * FROM upsert)`, as outlined in // http://www.maori.geek.nz/post/postgres_upsert_update_or_insert_in_ger_using_knex_js
* * SQLite - Implemented as two queries `INSERT; UPDATE`. This means that the update is executed regardless of whether the row already existed or not
*
* **Note** that SQLite returns undefined for created, no matter if the row was created or updated. This is because SQLite always runs INSERT OR IGNORE + UPDATE, in a single query, so there is no way to know whether the row was inserted or not.
*
* @param {Object} values
* @param {Object} values
* @param {Object} [options]
* @param {Object} [options]
* @param {Array} [options.fields=Object.keys(this.attributes)] The fields to insert / update. Defaults to all fields
*
*
* @return {Promise<created>} Returns a boolean indicating whether the row was created or updated.
* @return {Promise<created>} Returns a boolean indicating whether the row was created or updated.
*/
*/
Model.prototype.upsert=function(values,options){
Model.prototype.upsert=function(values,options){
options=options||{};
options=options||{};
// TODO - should we do a .build here to get default values + setters?
