diff --git a/node_modules/loopback-connector-postgresql/lib/discovery.js b/node_modules/loopback-connector-postgresql/lib/discovery.js
index 0393c52..6c6e8d4 100644
--- a/node_modules/loopback-connector-postgresql/lib/discovery.js
+++ b/node_modules/loopback-connector-postgresql/lib/discovery.js
@@ -335,6 +335,33 @@ function mixinDiscovery(PostgreSQL) {
     return sql;
   };
 
+  /**
+   * Discover unique keys for a given table
+   * @param {String} table The table name
+   * @param {Object} options The options for discovery
+   */
+
+  /*!
+   * Retrieves a list of column names that have unique key index
+   * @param schema
+   * @param table
+   * @returns {string}
+   */
+  PostgreSQL.prototype.buildQueryUniqueKeys = function(schema, table) {
+    const sql = 'SELECT a.attname AS "columnName", n.nspname AS "owner", c.relname AS "tableName" '
+      + 'FROM pg_index i '
+      + 'JOIN pg_class c ON c.oid = i.indrelid '
+      + 'JOIN pg_namespace n ON n.oid = c.relnamespace '
+      + 'JOIN pg_attribute a ON a.attrelid = c.oid AND a.attnum = ANY(i.indkey) '
+      + 'WHERE i.indisunique = true '
+      + 'AND i.indisprimary = false '
+      + 'AND n.nspname = \'' + schema + '\' '
+      + 'AND c.relname = \'' + table + '\' '
+      + 'ORDER BY a.attnum';
+    return sql;
+  };
+
+
   /**
    * Discover foreign keys that reference to the primary key of this table
    * @param {String} table The table name