document using BLOB data type for handler

[rjocoleman]

DDJob uses PHP's serialize() function to store data in the handler column.

From the PHP docs on serialize().

Note that this is a binary string which may include null bytes, and needs to be stored and handled as such. For example, serialize() output should generally be stored in a BLOB field in a database, rather than a CHAR or TEXT field.

https://php.net/manual/en/function.serialize.php#refsect1-function.serialize-returnvalues

A common symptom of this is errors like:

Notice: unserialize(): Error at offset 2010 of 2425 bytes in /var/www/magento/current/lib/DJJob/DJJob.php on line 454

I did not change the tests as they're using the MEMORY table type which is incompatible with BLOB.

[josegonzalez]

Why are you giving your jobs more data than record ids? Serializing a lot of data for a job seems like it's not the greatest idea?

[josegonzalez]

Note: I would also rather just note to our users that they may optionally use blob over text fields.

[rjocoleman]

Note: I would also rather just note to our users that they may optionally use blob over text fields.

I've adjusted this PR to be a note in the readme

[rjocoleman]

Serializing a lot of data for a job seems like it's not the greatest idea?

why not? I don't primarily live in a PHP/MySQL world so I looked to the docs for the solution to my unserialize() issue and stopped there.. I'm naively unaware of any other issues.

I've got JSON data being used for intra-app communication and DJJob processing this, as such the JSON is being serialized and living in handler until it's processed. Large is relative, I'm looking at data <10kB

[josegonzalez]

Thanks for changing the message.