如何在不实际执行的情况下获取由ActiveRecord #ref创建的SQL语句？

Question

我正在使用will_paginate一些复杂的查询,它无法正确计算总记录数(为了显示正确数量的页面链接) - 即由于多列分组.

因此,我打算获取SELECT查询,该查询将用于检索所有记录,而不实际执行它,并SELECT COUNT(*) FROM ...手动包装,以获取记录数.

有什么想法怎么做？

编辑:我正在使用Rails 2.3.x.

Answer 1

对于Rails 3:

在Rails 3文档中查看ActiveRecord :: Relation 文档.

# get the relation
rel = User.complex_scope.chained_complex_scope

# get the SQL
# this does not execute the query
sql = rel.to_sql

# find out how many records
# this executes the query behind the scenes
count = rel.size

Answer 2

看起来在Rails 2.x中,ActiveRecord::Base#construct_finder_sql可以使用一个名为的私有方法,我需要对它进行更多测试,看看它是否对我有用:

ActionType.find(:all, :select => 'hosted, top_action_type, count(*) as count', :group => 'hosted, top_action_type').count
#=> 6
sql = ActionType.send :construct_finder_sql, :select => 'hosted, top_action_type, count(*) as count', :group => 'hosted, top_action_type'
#=> "SELECT hosted, top_action_type, count(*) as count FROM "action_types"  GROUP BY hosted, top_action_type"
ActionType.count_by_sql "SELECT COUNT(*) FROM (#{sql}) a"
#=> 6