Rails query chokes on includes - mysql

Question

This query executes just fine:
p = PlayersToTeam.select("id").joins(:player).limit(10).order("players.FirstName")
This query causes my whole system to come to a screeching halt:
p = PlayersToTeam.select("id").includes(:player).limit(10).order("players.FirstName")
Here are the models:
class PlayersToTeam < ActiveRecord::Base
belongs_to :player
belongs_to :team
accepts_nested_attributes_for :player
end
class Player < ActiveRecord::Base
has_many :players_to_teams
has_many :teams, through: :players_to_teams
end
As far as I can tell, the includes does a LEFT JOIN and joins does an INNER JOIN. The query spit out (for joins) from Rails is:
SELECT players_to_teams.id FROM `players_to_teams` INNER JOIN `players` ON `players`.`id` = `players_to_teams`.`player_id` ORDER BY players.FirstName LIMIT 10
Which executes just fine on the command line.
SELECT players_to_teams.id FROM `players_to_teams` LEFT JOIN `players` ON `players`.`id` = `players_to_teams`.`player_id` ORDER BY players.FirstName LIMIT 10
also executes just fine, it just takes twice as long.
Is there an efficient way I can sort the players_to_teams records via players? I have an index on FirstName for players.
EDIT
Turns out the query required heavy optimization to run even half decently. Splitting the query was the best solution short of restructuring the Data or customizing the query

Answer 1

You also might consider to split it into 2(3) queries. First - to get ids by sorting with joins:
players_to_teams = PlayersToTeam.select("id").joins(:player).limit(10).order("players.FirstName")
Second (which is inside contains 2 queries) - to get PlayersToTeams with players pre-loaded.
players_to_teams = PlayersToTeam.include(:player).where(:id => players_to_teams.map(&:id))
So after that you will have fully initialized players_to_teams with players loaded and initialized.

Answer 2

One thing to note is that include will add a second db access to do the preloading. You should check what that one looks like (it should contain a big IN statement on the player_ids from players_to_teams).
As for how to avoid using include, if you just need the name from players, you can do it like this:
PlayersToTeam.select("players_to_teams.id, players.FirstName AS player_name").joins(:player).limit(10).order("players.FirstName")