Rails - Aug 2006 - using :select with :include to limit eager loading

Activerecord''s find option `:select'' does not appear to work
when
:include is used to eager load associations.  However, I sometimes want 
to perform ready-made joins on associations to limit the results of a 
query.  here''s a simple example:

table university:
STRING code
INT    id

table term:
STRING name
INT    university_id
INT    id

the associations of the models

University
has_many :terms

Term
belongs_to :university

if I want to select the terms with a given university, I can perform the 
straightforward function:

Term.find(:all, :include => :university, :conditions =>
"university.code
= ''stanford''")

however, this eager loads the university, which I have no use for.  In 
larger examples, many extra loads are performed that take a lot of ruby 
processing for information that is never used.  I have been able to 
improve performance by using the :joins option instead of :include, but 
the more intuitive rails method seems to use :select along with 
:include.  Am I missing something?  This doesn''t seem like the expected
behavior for the :select option.

-- 
Posted via http://www.ruby-forum.com/.

I have a hierarchical database structure where University > College > 
Department > Course, and I want to select several Course objects for a 
certain University.  I am achieving this now with a find() function that 
looks like this:

courses = Db::Course.find(:all, :include => {:department => {:school =>
:university}},
:conditions => ["university.title = ?",
''Stanford''],
:select => "course.code, course.id, department.code")

My query works, but the select clause doesn''t have any effect... it 
doesn''t show up in the query no matter what it is, and crazy values
like
''SDFASDF asdfASD FASD A'' do not raise a database error.

It is wasteful for me to select all the data from the joins when all I 
needed some of them for was to process certain conditions.  It is a very 
fast database operation no matter what but with large sets of data Ruby 
is slow to load the whole response.

am I don''t something wrong, or does activerecord need a fix?

thanks sincerely,

Red Daly


-- 
Posted via http://www.ruby-forum.com/.

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