from http://dev.mysql.com/doc/refman/4.1/en/blob.html
You can change the message buffer size by changing the value of the
max_allowed_packet variable, but you must do so for both the server and
your client program. For example, both mysql and mysqldump allow you to
change the client-side max_allowed_packet value.
Tom Lane wrote:
>>> If the use case is people running MySQL dumps, then there will be
>>> millions of values-targetlists in MySQL dumps.
>>>
>
> I did some experimentation just now, and could not get mysql to accept a
> command longer than about 1 million bytes. It complains about
> Got a packet bigger than 'max_allowed_packet' bytes
> which seems a bit odd because max_allowed_packet is allegedly set to
> 16 million, but anyway I don't think people are going to be loading any
> million-row tables using single INSERT commands in mysql either.
>
> regards, tom lane
>
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> TIP 5: don't forget to increase your free space map settings
>
>