Merge pull request #19984 from mcfiredrill/nodoc-change-column-null

:nodoc: change_column_null in the implmenting adapters

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -634,7 +634,7 @@ def change_column_default(table_name, column_name, default) #:nodoc:
         change_column table_name, column_name, column.sql_type, :default => default
       end
 
-      def change_column_null(table_name, column_name, null, default = nil)
+      def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
         column = column_for(table_name, column_name)
 
         unless null || default.nil?

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -438,7 +438,7 @@ def change_column_default(table_name, column_name, default) # :nodoc:
           end
         end
 
-        def change_column_null(table_name, column_name, null, default = nil)
+        def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
           clear_cache!
           unless null || default.nil?
             column = column_for(table_name, column_name)

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -450,7 +450,7 @@ def change_column_default(table_name, column_name, default) #:nodoc:
         end
       end
 
-      def change_column_null(table_name, column_name, null, default = nil)
+      def change_column_null(table_name, column_name, null, default = nil) #:nodoc:
         unless null || default.nil?
           exec_query("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
         end