MySQL 5.7 Release Notes
INSERT DELAYED ...
The DELAYED option for the
INSERT statement is a MySQL
extension to standard SQL. In previous versions of MySQL, it can
be used for certain kinds of tables (such as
MyISAM), such that when a client uses
INSERT DELAYED, it gets an okay
from the server at once, and the row is queued to be inserted
when the table is not in use by any other thread.
DELAYED inserts and replaces were deprecated
in MySQL 5.6.6. In MySQL 5.7,
DELAYED is not supported. The server
recognizes but ignores the DELAYED keyword,
handles the insert as a nondelayed insert, and generates an
ER_WARN_LEGACY_SYNTAX_CONVERTED warning
(“INSERT DELAYED is no longer supported. The statement was
converted to INSERT”). The DELAYED
keyword is scheduled for removal in a future release.
lock table lt2 write;
insert delayed into lt2 (t) values ('123');
-- Error Code : 1165
-- INSERT DELAYED can't be used with table 'lt2' because it is locked with LOCK TABLES
INSERT DELAYED is treated as normal INSERT if a column has defined TRIGGER (AFTER or BEFORE INSERT).
I found a bug about that and some comment regarding missing doc info, about this behaviour: http://bugs.mysql.com/bug.php?id=32220