Question

I have the problem that the query I use for finder_sql is not parsed correctly before it is handed over to PostgreSQL resulting in a database syntax error.

To illustrate the problem I just used the example code from here:

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

I only changed class_name to "User" as I don’t have a person model but this does not matter here.

has_many :subscribers, :class_name => "User", :finder_sql =>
'SELECT DISTINCT people.* ' +
'FROM people p, post_subscriptions ps ' +
'WHERE ps.post_id = #{id} AND ps.person_id = p.id ' +
'ORDER BY p.first_name'

When I use this, I get the following error:

User Load (0.3ms)  SELECT DISTINCT people.* FROM people p, post_subscriptions ps WHERE
ps.post_id = #{id} AND ps.person_id = p.id ORDER BY p.first_name
PGError: ERROR:  Syntaxerror near »{« 
LINE 1: ...ople p, post_subscriptions ps WHERE ps.post_id = #{id} AND p...
                                                         ^

As you can see #{id} is not replaced with the id of the object which then raises the PostgreSQL error.

Environment

• Rails 3.1
• rvm
• PostgreSQL 9.1
• Ubuntu 11.10
• Ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-linux]

Answer 1

I think what you’re actually looking for is this:

has_many :posts, :finder_sql =>
    proc {"SELECT p.* from posts p join topics t on p.topic_id = t.id where t.id=#{id}"}

As of Rails 3.1 you have to use a proc instead of a string to use fields like #{id}.

See the issue here: https://github.com/rails/rails/issues/3920