Revert "Revert "Generate proper :counter_sql from :finder_sql when there is a newline character immediately following 'SELECT' [#2118 state:resolved]""

This reverts commit 80f1f863cd0f9cba89079511282de5710a2e1832.

The feature doesn't work on Postgres, so don't test it on Postgres.
Also, Postgres compatibility is irrelevant to the ticket/patch in question.

1 files changed, 13 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index e12f6be35d..84edaec15e 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -351,7 +351,19 @@ module ActiveRecord
       protected
         def construct_find_options!(options)
         end
-        
+
+        def construct_counter_sql
+          if @reflection.options[:counter_sql]
+            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
+          elsif @reflection.options[:finder_sql]
+            # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
+            @reflection.options[:counter_sql] = @reflection.options[:finder_sql].sub(/SELECT\b(\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
+            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
+          else
+            @counter_sql = @finder_sql
+          end
+        end
+
         def load_target
           if !@owner.new_record? || foreign_key_present
             begin