MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide

13.2.5.3 INSERT DELAYED Syntax

INSERT DELAYED ...

The DELAYED option for the INSERT statement is a MySQL extension to standard SQL that can be used for certain kinds of tables (such as MyISAM). 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.

Note

INSERT DELAYED is slower than a normal INSERT if the table is not otherwise in use. There is also the additional overhead for the server to handle a separate thread for each table for which there are delayed rows. This means that you should use INSERT DELAYED only when you are really sure that you need it.

As of MySQL 5.6.6, INSERT DELAYED is deprecated, and will be removed in a future release. Use INSERT (without DELAYED) instead.

The queued rows are held only in memory until they are inserted into the table. This means that if you terminate mysqld forcibly (for example, with kill -9) or if mysqld dies unexpectedly, any queued rows that have not been written to disk are lost.

There are some constraints on the use of DELAYED:

The following describes in detail what happens when you use the DELAYED option to INSERT or REPLACE. In this description, the thread is the thread that received an INSERT DELAYED statement and handler is the thread that handles all INSERT DELAYED statements for a particular table.