Change user prefs search logic to use index (#2644)

Sadly, array index failed to cover "unset bits" case,
so excluded bits are merged into bigint, and &'d with column,
which turned out more readable and simpler than bit string.

app/models/user.rb

@@ -759,7 +759,6 @@ class User < ActiveRecord::Base
         q = q.where("id in (?)", params[:id].split(",").map(&:to_i))
       end
 
-      bitprefs_length = BOOLEAN_ATTRIBUTES.length
       bitprefs_include = nil
       bitprefs_exclude = nil
 
@@ -767,25 +766,21 @@ class User < ActiveRecord::Base
         if params[x].present?
           attr_idx = BOOLEAN_ATTRIBUTES.index(x.to_s)
           if params[x] == "true"
-            bitprefs_include ||= "0"*bitprefs_length
-            bitprefs_include[attr_idx] = '1'
+            bitprefs_include ||= []
+            bitprefs_include << attr_idx
           elsif params[x] == "false"
-            bitprefs_exclude ||= "0"*bitprefs_length
-            bitprefs_exclude[attr_idx] = '1'
+            bitprefs_exclude ||= 0
+            bitprefs_exclude |= (1 << attr_idx)
           end
         end
       end
-
+      
       if bitprefs_include
-        bitprefs_include.reverse!
-        q = q.where("bit_prefs::bit(:len) & :bits::bit(:len) = :bits::bit(:len)",
-                    {:len => bitprefs_length, :bits => bitprefs_include})
+        q = q.where("bit_position_array(bit_prefs) @> ARRAY[?]::integer[]", bitprefs_include)
       end
-
+      
       if bitprefs_exclude
-        bitprefs_exclude.reverse!
-        q = q.where("bit_prefs::bit(:len) & :bits::bit(:len) = 0::bit(:len)",
-                    {:len => bitprefs_length, :bits => bitprefs_exclude})
+        q = q.where("bit_prefs & ? = 0", bitprefs_exclude)
       end
 
       if params[:current_user_first] == "true" && !CurrentUser.is_anonymous?