let tableName = 'user_meta';
let conflictTarget = 'login';
let itemData = {
  login: 'plurch',
  user_id: 3332519
};

let resultPromise = upsertItem(tableName, conflictTarget, itemData);

resultPromise.then(userMeta => console.log('Processed this user: ' + userMeta.login));

// 
// This query will be generated:
// 
// insert into "user_meta" ("login", "user_id") values ('plurch', '3332519') ON CONFLICT ("login") DO UPDATE SET "user_id" = EXCLUDED."user_id" RETURNING *;
//