Fix change_column to work with postgres 7.x and 8.x.

Closes #3141


git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3327 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 22 insertions, 11 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 45ef990ddb..d5c7948009 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,12 +1,6 @@
 *SVN*
 
-* removed :piggyback in favor of just allowing :select on :through associations. [Tobias Luetke]
-
-* made method missing delegation to class methods on relation target work on :through associations. [Tobias Luetke]
-
-* made .find() work on :through relations. [Tobias Luetke]
-
-* added :piggyback option to has_many :through relationships to pick up values from the join table as needed [Tobias Luetke] 
+* Fix change_column to work with PostgreSQL 7.x and 8.x.  #3141 [wejn@box.cz, Rick Olson, Scott Barron] 
 
 * Fix typo in association docs. #3296. [Blair Zajac]
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index e3059ea010..fbb978e034 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -302,7 +302,17 @@ module ActiveRecord
       end
 
       def change_column(table_name, column_name, type, options = {}) #:nodoc:
-        execute = "ALTER TABLE #{table_name} ALTER  #{column_name} TYPE #{type}"
+        begin
+          execute "ALTER TABLE #{table_name} ALTER  #{column_name} TYPE #{type_to_sql(type, options[:limit])}"
+        rescue ActiveRecord::StatementInvalid
+          # This is PG7, so we use a more arcane way of doing it.
+          begin_db_transaction
+          add_column(table_name, "#{column_name}_ar_tmp", type, options)
+          execute "UPDATE #{table_name} SET #{column_name}_ar_tmp = CAST(#{column_name} AS #{type_to_sql(type, options[:limit])})"
+          remove_column(table_name, column_name)
+          rename_column(table_name, "#{column_name}_ar_tmp", column_name)
+          commit_db_transaction
+        end
         change_column_default(table_name, column_name, options[:default]) unless options[:default].nil?
       end      
 
diff --git a/activerecord/test/migration_test.rb b/activerecord/test/migration_test.rb
index 3fa680b94a..8d8deb8026 100644
--- a/activerecord/test/migration_test.rb
+++ b/activerecord/test/migration_test.rb
@@ -31,7 +31,7 @@ if ActiveRecord::Base.connection.supports_migrations?
       Person.connection.remove_column("people", "administrator") rescue nil
       Person.reset_column_information
     end
-    
+
     def test_add_index
       Person.connection.add_column "people", "last_name", :string        
       Person.connection.add_column "people", "administrator", :boolean
@@ -258,8 +258,15 @@ if ActiveRecord::Base.connection.supports_migrations?
     end
 
     def test_change_column
-      Person.connection.add_column "people", "bio", :string
-      assert_nothing_raised { Person.connection.change_column "people", "bio", :text }
+      Person.connection.add_column 'people', 'age', :integer
+      old_columns = Person.connection.columns(Person.table_name, "#{name} Columns")
+      assert old_columns.find { |c| c.name == 'age' and c.type == :integer }
+
+      assert_nothing_raised { Person.connection.change_column "people", "age", :string }
+      
+      new_columns = Person.connection.columns(Person.table_name, "#{name} Columns")
+      assert_nil new_columns.find { |c| c.name == 'age' and c.type == :integer }
+      assert new_columns.find { |c| c.name == 'age' and c.type == :string }
     end    
 
     def test_change_column_with_new_default