Don't use a subquery when there are joins. Use a required alias for t…

…he subquery.
rails · Jun 23, 2010 · a040b1c · a040b1c
1 parent 71e9299
commit a040b1c
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Showing 2 changed files with 8 additions and 7 deletions.
diff --git a/lib/arel/engines/sql/relations/compiler.rb b/lib/arel/engines/sql/relations/compiler.rb
@@ -8,9 +8,10 @@ def initialize(relation)
       end
 
       def select_sql
-        if relation.projections.first.is_a?(Count) && relation.projections.size == 1 && (taken.present? || wheres.present?)
+        if relation.projections.first.is_a?(Count) && relation.projections.size == 1 &&
+          (taken.present? || wheres.present?) && joins(self).blank?
           subquery = build_query("SELECT 1 FROM #{from_clauses}", build_clauses)
-          query = "SELECT #{select_clauses.join(', ')} FROM (#{subquery})"
+          query = "SELECT COUNT(*) AS count_id FROM (#{subquery}) AS subquery"
         else
           query = build_query \
             "SELECT     #{select_clauses.join(', ')}",
@@ -27,8 +28,8 @@ def build_clauses
           ("GROUP BY  #{group_clauses.join(', ')}"       unless groupings.blank?   ),
           ("HAVING    #{having_clauses.join(' AND ')}"      unless havings.blank?     ),
           ("ORDER BY  #{order_clauses.join(', ')}"       unless orders.blank?      )
-        clauses << " #{locked}" unless locked.blank?
         engine.add_limit_offset!(clauses,{ :limit => taken, :offset => skipped }) if taken || skipped
+        clauses << " #{locked}" unless locked.blank?
         clauses unless clauses.blank?
       end
 

diff --git a/spec/engines/sql/unit/relations/take_spec.rb b/spec/engines/sql/unit/relations/take_spec.rb
@@ -58,15 +58,15 @@ module Arel
 
         adapter_is :mysql do
           sql.should be_like(%Q{
-            SELECT COUNT(`users`.`id`) AS count_id
-            FROM (SELECT 1 FROM `users` LIMIT 4)
+            SELECT COUNT(*) AS count_id
+            FROM (SELECT 1 FROM `users` LIMIT 4) AS subquery
           })
         end
 
         adapter_is_not :mysql, :oracle do
           sql.should be_like(%Q{
-            SELECT COUNT("users"."id") AS count_id
-            FROM (SELECT 1 FROM "users" LIMIT 4)
+            SELECT COUNT(*) AS count_id
+            FROM (SELECT 1 FROM "users" LIMIT 4) AS subquery
           })
         end
       end