respect auto_increment in rename_column for mysql

6 files changed, 27 insertions, 11 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 16460ec36d..a537d8cdc1 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   `rename_column` preserves auto_increment in mysql migrations.
+    Fixes #3493.
+
+    *Vipul A M*
+
 *   PostgreSQL geometric type point is supported by ActiveRecord. Fixes #7324.
 
     *Martin Schuerrer*
@@ -24,7 +29,7 @@
 
     *Ian Young*
 
-*   If ``:inverse_of` is true on an association, then when one calls `find()` on
+*   If `:inverse_of` is true on an association, then when one calls `find()` on
     the association, Active Record will first look through the in-memory objects
     in the association for a particular id. Then, it will go to the DB if it
     is not found. This is accomplished by calling `find_by_scan` in
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 26cacbde37..984081fa28 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -688,6 +688,9 @@ module ActiveRecord
         if options[:null] == false
           sql << " NOT NULL"
         end
+        if options[:auto_increment] == true
+          sql << " AUTO_INCREMENT"
+        end
       end
 
       # SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 71f5c8fd29..b6bb8e0dc9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -25,12 +25,12 @@ module ActiveRecord
       end
 
       class Column < ConnectionAdapters::Column # :nodoc:
-        attr_reader :collation, :strict
+        attr_reader :collation, :strict, :extra
 
-        def initialize(name, default, sql_type = nil, null = true, collation = nil, strict = false)
+        def initialize(name, default, sql_type = nil, null = true, collation = nil, strict = false, extra = "")
           @strict    = strict
           @collation = collation
-
+          @extra     = extra
           super(name, default, sql_type, null)
         end
 
@@ -217,8 +217,8 @@ module ActiveRecord
       end
 
       # Overridden by the adapters to instantiate their specific Column type.
-      def new_column(field, default, type, null, collation) # :nodoc:
-        Column.new(field, default, type, null, collation)
+      def new_column(field, default, type, null, collation, extra = "") # :nodoc:
+        Column.new(field, default, type, null, collation, extra)
       end
 
       # Must return the Mysql error number from the exception, if the exception has an
@@ -448,7 +448,7 @@ module ActiveRecord
         sql = "SHOW FULL FIELDS FROM #{quote_table_name(table_name)}"
         execute_and_free(sql, 'SCHEMA') do |result|
           each_hash(result).map do |field|
-            new_column(field[:Field], field[:Default], field[:Type], field[:Null] == "YES", field[:Collation])
+            new_column(field[:Field], field[:Default], field[:Type], field[:Null] == "YES", field[:Collation], field[:Extra])
           end
         end
       end
@@ -682,6 +682,7 @@ module ActiveRecord
         if column = columns(table_name).find { |c| c.name == column_name.to_s }
           options[:default] = column.default
           options[:null] = column.null
+          options[:auto_increment] = (column.extra == "auto_increment")
         else
           raise ActiveRecordError, "No such column: #{table_name}.#{column_name}"
         end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index 25b8aef617..6b319fed88 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -63,8 +63,8 @@ module ActiveRecord
         end
       end
 
-      def new_column(field, default, type, null, collation) # :nodoc:
-        Column.new(field, default, type, null, collation, strict_mode?)
+      def new_column(field, default, type, null, collation, extra = "") # :nodoc:
+        Column.new(field, default, type, null, collation, strict_mode?, extra)
       end
 
       def error_number(exception)
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 7544c2a783..0e01fe0fdb 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -150,8 +150,8 @@ module ActiveRecord
         end
       end
 
-      def new_column(field, default, type, null, collation) # :nodoc:
-        Column.new(field, default, type, null, collation, strict_mode?)
+      def new_column(field, default, type, null, collation, extra = "") # :nodoc:
+        Column.new(field, default, type, null, collation, strict_mode?, extra)
       end
 
       def error_number(exception) # :nodoc:
diff --git a/activerecord/test/cases/migration/columns_test.rb b/activerecord/test/cases/migration/columns_test.rb
index e52809f0f8..52906c8a01 100644
--- a/activerecord/test/cases/migration/columns_test.rb
+++ b/activerecord/test/cases/migration/columns_test.rb
@@ -62,6 +62,13 @@ module ActiveRecord
         assert_equal 70000, default_after
       end
 
+      if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
+        def test_mysql_rename_column_preserves_auto_increment
+          rename_column "test_models", "id", "id_test"
+          assert_equal "auto_increment", connection.columns("test_models").find { |c| c.name == "id_test" }.extra
+        end
+      end
+
       def test_rename_nonexistent_column
         exception = if current_adapter?(:PostgreSQLAdapter, :OracleAdapter)
                       ActiveRecord::StatementInvalid