Is there a limit to the length/size of serialized data that can be stored as user meta?

I tried to store an array containing about 50000 keys and respective values to the user meta using update_user_meta. Since, this was only a test, I ran a for loop to generate the array.

$test = array ();
for ($i = 0; $i <= 50000; $i++) {
    $test[$i] = $i;
}
update_user_meta($user_id, 'test', $test);

I ended up getting the error WordPress database error: [MySQL server has gone away]. Eventually, I was able to get it working with an array size of 48000 keys. Since update_user_meta converts arrays to serialized data before storing, is there a limit to the serialized data that user meta or post metas can handle? Or does this happen due to some other issue?

I tried the timeout fix suggested here. But I am not sure if it is supposed to work for WP 3.3.1. or whether if at all it is solution to my problem.

Please note I am using a local dev install using MAMP.

Answers:

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Method 1

According to the DB schemea, the meta_value column is of type longtext, and that has a maximum size of 4GB, however you’re unlikely to reach that.

Eitherway storing large quantities of data in a single field is bad both from a practical point of view, a performance point of view, and data storage.

I advise instead you use a custom taxonomy for this kind of data ( yes taxonomies aren’t just for post objects )

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