File: README — Documentation for slim-attributes (0.7.6)

SlimAttributes

This is a small patch to the ActiveRecord Mysql adaptor that stops rails from using the all_hashes / each_hash mechanism - which is what is called when you do a find.

It is faster, and uses less memory.

Measuring with just ActiveRecord code - fetching stuff from the database - we see anything up to a 50% (or more) speed increase, but I suppose it really depends on your system and environment, and what you are doing with the results from the database. The more columns your tables have, the better the improvement will likely be. Measure your own system and send me the results!

Installation

Slim attributes works with ruby 1.8.x. Ruby 1.9 support exists, but a bug in rails prevents it working (see Bugs for further info).

Try: sudo gem install slim-attributes or: sudo gem install slim-attributes – –with-mysql-config

then add this to environment.rb: require ‘slim_attributes’

Description

The reason for overriding all_hashes is threefold:

making a hash of each and every row returned from the database is slow
ruby makes frozen copies of each column name string (for the keys) which results in a great many strings which are not really needed
we observe that it’s not often that all the fields of rows fetched from the database are actually used

So this is an alternative implementation of all_hashes that returns a ‘fake hash’ which contains a hash of the column names (the same hash of names is used for every row), and also contains the row data in an area memcpy’d directly from the mysql API.

The field contents are then instantiated into Ruby strings on demand - ruby strings are only made if you need them. Note that if you always look at all the columns when you fetch data from the database then this won’t necessarily be faster that the unpatched mysql adapter. But it won’t be much slower either, and we do expect that most times not all the columns from a result set are accessed.

Bugs

Slim attributes will not work correctly with rails and ruby 1.9.1 until Rails 2.3.5 is released due to this ticket: rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/3156-mysql_adapterrb-redefines-all_hashes-multiple-times-under-ruby-19

Warranty

No warranty - this gem has been extensively tested, but not in all environments.

We are using it in our production environment with very good results. Please report bugs to sdsykes at symbol gmail pip com or via the github issue tracking system.

Credits

Thanks to IronDigital for the initial port for ruby 1.9. Thanks to Greg Hazel for fixing compilation for windows.