what is bigger than a longblob?
Using LONGBLOB can be very risky in light of the fact that the biggest max_allowed_packet is only 1GB.

Back in August 2006, someone asked a similar question. in which Peter Zaitsev said:


  http://dev.mysql.com/doc/refman/5.0/en/storage-requirements.html
  
  As you can see in theory it is about 4GB.
  
  It is however also limited by max_packet_size which is 16M by default.
  
  I would be very careful using blobs larger than 100MB.   MySQL will
  need some 3 times of this size of memory allocated on the server for
  blob processing.


I am not a PostgreSQL DBA, but I would have to venture the following suggestion:


If you must store objects that big, you should go with PostgreSQL because it has a storage infrastructure called the The Outside Attribute Storage Technique (TOAST). This allows rows not to be too big for SQL processing.
If you must use MySQL, you are much better off storing URL File Links than the BLOB itself.