The release notes here are organized by release. For a list of changes see the See CHANGELOG file. In this file are the steps to take to aid in keeping things rolling after updating to the latest version.


This release included a new cache that performs better than the earlier cache and a new high performance parser.


The new cache includes a least recently used expiration to reduce memory use. The cache is also self adjusting and will expand as needed for better performance. It also handles Hash keys and string values with two options, :cache_keys, a boolean and :cache_str an integer. The :cache_str if set to more than zero is the limit for the length of string values to cache. The maximum value is 35 which allows strings up to 34 bytes to be cached.

One interesting aspect of the cache is not so much the string caching which performs similar to the Ruby intern functions but the caching of symbols and object attribute names. There is a significant gain for symbols and object attributes.

If the cache is not desired then setting the default options to turn it off can be done with this line:

Oj.default_options = { cache_keys: false, cache_str: 0 }


The new parser uses a different core that follows the approach taken by OjC and OjG. It also takes advantage of the bulk Array and Hash functions. Another issue the new parser addresses is option management. Instead of a single global default_options each parser instance maintains it's own options.

There is a price to be paid when using the Oj::Parser. The API is not the same the older parser. A single parser can only be used in a single thread. This allows reuse of internal buffers for additional improvements in performance.

The performane advantage of the Oj::Parse is that it is more than 3 times faster than the Oj::compat_load call and 6 times faster than the JSON gem.

Dump Performance

Thanks to Watson1978 Oj.dump also received a speed boost.