Question

When querying the database with:

@robots = Robot.all(:condition => [:a => 'b'], :limit => 50, :offset => 0)

What is the best way to get the total number of rows without the :limit?

In raw MySQL you could do something like this:

SELECT SQL_CALC_FOUND_ROWS * FROM robots WHERE a=b LIMIT 0, 50
SELECT FOUND_ROWS();

Is there an active record way of doing this?

Answer 1

Robot.count actually is the solution you want.

Reading one of the comments above, it looks like you may have a misunderstanding of how .count works. It returns a count of all the rows in the table only if there’s no parameters.

but if you pass in the same conditions that you pass to all/find eg:

Robot.count(:conditions => {:a => 'b'})

.count() will return the number of rows that match the given conditions.
Just to be obvious – you can even save the condition-hash as a variable to pass into both – to reduce duplication, so:

conds = {:a => 'b'}
@robots = Robot.all(:conditions => conds, :limit => 50)
@num_robots = Robot.count(:conditions => conds)

That being said – you can’t do an after-the-fact count on the result-set (like in your example). ie you can’t just run your query then ask it how many rows would have been found. You do actually have to call .count on purpose.