How to store long text to MySql DB using Rails?
I don't know if rails supported :longtext officially in previous versions, but in the current version according to rails documentation, :longtext is in fact not specified as legal datatype. I think it's only a convenience of the mysql adapter that translates this to :text.
The correct way to do it is then:
change_column :contents, :description, :text, :limit => 4294967295
Keep it mind that the effective maximum size is less when using multi-byte characters.
Edit: Thinking a second about it and it makes sense that rails halves the size. Re-reading the mysql docs on this topic , they speak of effective size. I guess specifying 2147483647 could lead to an effective size of 4294967295 when filled with 2-byte UTF-8 characters. As UTF-8 is the default encoding in ruby 1.9 (at least on my machine), it's the only correct way to do it. I think?!
ruby-1.9.2-p136 :002 > "".encoding=> #<Encoding:UTF-8>