Finding recently next matches's players by category

gistfile1.rb

#"SELECT "matches".* FROM "matches" WHERE "matches"."id" 
#IN (
#	SELECT MIN("matches"."id") AS min_id FROM "pairs" INNER JOIN "matches" 
#		ON ("pairs"."player_id" = 14 OR "pairs"."partner_id" = 14) AND ("pairs"."id" =      #"matches"."first_pair_id" OR "pairs"."id" = "matches"."second_pair_id") AND "matches"."winner_pair" IS NULL AND 			#"matches"."wo_pair" IS NULL AND ("matches"."start_date" IS NULL OR "matches"."start_date" >= '2011-10-30 #21:09:48.398210') GROUP BY "matches"."category_id")" 
class Player < ActiveRecord::Base 
 def planning_matches
    matches = Match.arel_table
    pairs = Pair.arel_table
    condition = (pairs[:player_id].eq(self.id).or(pairs[:partner_id].eq(self.id)))
                .and(pairs[:id].eq(matches[:first_pair_id]).or(pairs[:id].eq(matches[:second_pair_id]))
                .and(matches[:winner_pair].eq(nil).and(matches[:wo_pair].eq(nil)))
                .and(matches[:start_date].eq(nil).or(matches[:start_date].gteq(Time.now)))
                )
    Match.where(:id =>    Pair.select(matches[:id].minimum).joins(:matches).on(condition).group(matches[:category_id]))
 end
end