row0sel.c:

  Fix bug #8677: if one used LOCK TABLES, created an InnoDB temp table, and did a multi-table update where a MyISAM table was the update table and the temp table was a read table, then InnoDB aserted in row0sel.c because n_mysql_tables_in_use was 0. Also, we remove the assertion altogether and just print an error to the .err log if this important consistency check fails. Then it is up to the user to read the .err log and notice the problem if there still are errors in MySQL's table locking.

innobase/row/row0sel.c

@@ -2912,14 +2912,19 @@ row_search_for_mysql(
 		ut_error;
 	}
 
-	if (trx->n_mysql_tables_in_use == 0) {
+	if (trx->n_mysql_tables_in_use == 0
+            && prebuilt->select_lock_type == LOCK_NONE) {
+		/* Note that if MySQL uses an InnoDB temp table that it
+		created inside LOCK TABLES, then n_mysql_tables_in_use can
+		be zero; in that case select_lock_type is set to LOCK_X in
+		::start_stmt. */
+
 		fputs(
 "InnoDB: Error: MySQL is trying to perform a SELECT\n"
 "InnoDB: but it has not locked any tables in ::external_lock()!\n",
                       stderr);
 		trx_print(stderr, trx);
                 fputc('\n', stderr);
-		ut_a(0);
 	}
 
 /*	fprintf(stderr, "Match mode %lu\n search tuple ", (ulong) match_mode);