The following bug has been logged on the website:
Bug reference: 12202
Logged by: Matt Freeman
Email address: matt@nonuby.com
PostgreSQL version: 9.4beta1
Operating system: Ubuntu 14.10 64bit
Description:
I am just going to link to the stackoverflow post, as it contains both the
question and an answer which helps clarify the problem, I fear pasting as-is
here might be confusing.
http://stackoverflow.com/questions/27415340/postgresql-offset-behavior-with-json-column?noredirect=1#comment43279635_27415340
tl;dr When using offset, postgres seems to want to unserialize the json data
for every row it's visiting.
