Track NO_BACKSLASH_ESCAPES

Track NO_BACKSLASH_ESCAPES in case it is changed:
- using SET sql_mode by the client
- directly on the backend (for example default sql_mode, or an
  sql_mode set from another variable)

lib/MySQL_Session.cpp

@@ -5645,6 +5645,16 @@ bool MySQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
 					auto values = std::begin(it->second);
 					if (var == "sql_mode") {
 						std::string value1 = *values;
+						if (strcasecmp(value1.c_str(),"NO_BACKSLASH_ESCAPE") != 0) {
+							// client is setting NO_BACKSLASH_ESCAPE in sql_mode
+							// Because we will reply with an OK packet without
+							// first setting sql_mode to the backend (this is
+							// by design) we need to set no_backslash_escapes
+							// in the client connection
+							if (client_myds && client_myds->myconn) { // some extra sanity check
+								client_myds->myconn->set_no_backslash_escapes(true);
+							}
+						}
 						if (
 							( strcasecmp(value1.c_str(),(char *)"CONCAT") == 0 )
 							||

lib/mysql_connection.cpp

@@ -2537,6 +2537,17 @@ void MySQL_Connection::ProcessQueryAndSetStatusFlags(char *query_digest_text) {
 			set_status(false, STATUS_MYSQL_CONNECTION_HAS_SAVEPOINT);
 		}
 	}
+	if (mysql) {
+		if (myds && myds->sess) {
+			if (myds->sess->client_myds && myds->sess->client_myds->myconn) {
+				// if SERVER_STATUS_NO_BACKSLASH_ESCAPES is changed it is likely
+				// because of sql_mode was changed
+				// we set the same on the client connection
+				unsigned int ss = mysql->server_status & SERVER_STATUS_NO_BACKSLASH_ESCAPES;
+				myds->sess->client_myds->myconn->set_no_backslash_escapes(ss);
+			}
+		}
+	}
 }
 
 void MySQL_Connection::optimize() {