Support custom SQL query option

.gitignore

@@ -23,3 +23,7 @@ pkg
 
 ## PROJECT::SPECIFIC
 .project
+
+# RVM files
+.ruby-version
+.ruby-gemset

README.md

@@ -97,6 +97,18 @@ Which will generate the following SQL command:
 COPY (SELECT name FROM "users" WHERE "users"."id" IN (1, 2, 3)) TO '/tmp/users.csv' WITH DELIMITER ',' CSV HEADER
 ```
 
+Alternatively, you can supply customized raw SQL query to copy_to instead of scoped relation:
+
+```ruby
+User.copy_to("/tmp/users.csv", query: 'SELECT count(*) as Total FROM users')
+```
+
+Which will generate the following SQL command:
+
+```sql
+COPY (SELECT count(*) as Total FROM users) TO '/tmp/users.csv' WITH DELIMITER ',' CSV HEADER
+```
+
 The COPY command also supports exporting the data in binary format.
 
 ```ruby

lib/postgres-copy/acts_as_copy_target.rb

@@ -16,12 +16,13 @@ def copy_to path = nil, options = {}
                          else
                            "DELIMITER '#{options[:delimiter]}' CSV #{options[:header] ? 'HEADER' : ''}"
                          end
+        options_query = options.delete(:query) || self.all.to_sql
 
         if path
           raise "You have to choose between exporting to a file or receiving the lines inside a block" if block_given?
-          connection.execute "COPY (#{self.all.to_sql}) TO '#{sanitize_sql(path)}' WITH #{options_string}"
+          connection.execute "COPY (#{options_query}) TO '#{sanitize_sql(path)}' WITH #{options_string}"
         else
-          connection.raw_connection.copy_data "COPY (#{self.all.to_sql}) TO STDOUT WITH #{options_string}" do
+          connection.raw_connection.copy_data "COPY (#{options_query}) TO STDOUT WITH #{options_string}" do
             while line = connection.raw_connection.get_copy_data do
               yield(line) if block_given?
             end

spec/copy_to_spec.rb

@@ -5,7 +5,7 @@
     ActiveRecord::Base.connection.execute %{
       TRUNCATE TABLE test_models;
       SELECT setval('test_models_id_seq', 1, false);
-}
+    }
     TestModel.create :data => 'test data 1'
   end
 
@@ -79,5 +79,11 @@
         end
       end.should raise_error
     end
+
+    it "accepts custom sql query to run instead on the current relation" do
+      TestModel.copy_to '/tmp/export.csv', query: 'SELECT count(*) as "Total" FROM test_models'
+      content = File.open('/tmp/export.csv', 'r').read
+      expect(content).to eq("Total\n1\n")
+    end
   end
 end