How can I increase a field in a rails gem?

How can I increase a field in a rails gem?

References

Reference NO 1

http://stackoverflow.com/questions/15194261/how-can-i-increase-a-field-in-a-rails-gem

Reference NO 2

http://stackoverflow.com/questions/9535093/using-gem-unread-with-public-activity

Reference NO 3

https://github.com/sunspot/sunspot

Reference NO 4

http://blog.artlogic.com/2012/09/13/custom-fields-in-rails/

Reference NO 5

http://edgeguides.rubyonrails.org/active_record_querying.html

Reference NO 6

http://rakeroutes.com/blog/increase-rails-performance-with-database-indexes

Reference NO 7

#EANF#

Reference NO 8

#EANF#