row0sel.c Disable a special join speed optimization until Peter Zaitsev's hang is tracked down

innobase/row/row0sel.c

@@ -2537,7 +2537,10 @@ row_search_for_mysql(
 
 		unique_search_from_clust_index = TRUE;
 
-		if (trx->mysql_n_tables_locked == 0
+		/* Disable this optimization (hence FALSE below) until
+		the hang of Peter Zaitsev has been tracked down */
+
+		if (FALSE && trx->mysql_n_tables_locked == 0
 					&& !prebuilt->sql_stat_start) {
 
 			/* This is a SELECT query done as a consistent read,