ColumnsOnDemand
===============

Lazily loads large columns on demand.

By default, does this for all TEXT (:text) and BLOB (:binary) columns, but a list
of specific columns to load on demand can be given.

This is useful to reduce the memory taken by Rails when loading a number of records
that have large columns if those particular columns are actually not required most
of the time.  In this situation it can also greatly reduce the database query time
because loading large BLOB/TEXT columns generally means seeking to other database
pages since they are not stored wholly in the record's page itself.

Although this plugin is mainly used for BLOB and TEXT columns, it will actually
work on all types - and is just as useful for large string fields etc.


Compatibility
=============

Supports mysql, mysql2, postgresql, and sqlite3.

Currently tested against Rails 4.2.1, 4.2.0, 4.1.5, 4.0.9, 3.2.18, on Ruby 2.1.5.

Was also previously tested compatible with 2.3.14, 3.0.17, and 3.1.8 on Ruby 2.0.0
or 1.8.7 as appropriate, and may still work for them.


Example
=======

# Example.all will exclude the file_data and processing_log columns from the
# SELECT query, and example.file_data and example.processing_log will load & cache
# that individual column value for the record instance.
class Example
  columns_on_demand :file_data, :processing_log
end

# Scans the 'examples' table columns and registers all TEXT (:text) and BLOB (:binary)
# columns for loading on demand.
class Example
  columns_on_demand
end


Copyright (c) 2008-2015 Will Bryant, Sekuda Ltd, released under the MIT license