Re-implement our own columns cache since we have to use it excessively with the query_requires_identity_insert?

  * At some point rails will start using #exec_query more which has the binds
    and hence we can tell if the query requires and id insert by reflecting
    on the binds columns vs raw SQL regexp and columns calls.

Author: metaskills

lib/active_record/connection_adapters/sqlserver/schema_statements.rb

@@ -44,16 +44,31 @@ def indexes(table_name, name = nil)
 
         def columns(table_name, name = nil)
           return [] if table_name.blank?
-          column_definitions(table_name).collect do |ci|
+          @sqlserver_columns_cache[table_name] ||= column_definitions(table_name).collect do |ci|
             sqlserver_options = ci.except(:name,:default_value,:type,:null).merge(:database_year=>database_year)
             SQLServerColumn.new ci[:name], ci[:default_value], ci[:type], ci[:null], sqlserver_options
           end
         end
 
+        def create_table(table_name, options = {})
+          super
+          clear_cache!
+        end
+        
         def rename_table(table_name, new_name)
           do_execute "EXEC sp_rename '#{table_name}', '#{new_name}'"
         end
+        
+        def drop_table(table_name, options = {})
+          super
+          clear_cache!
+        end
 
+        def add_column(table_name, column_name, type, options = {})
+          super
+          clear_cache!
+        end
+        
         def remove_column(table_name, *column_names)
           raise ArgumentError.new("You must specify at least one column name.  Example: remove_column(:people, :first_name)") if column_names.empty?
           column_names.flatten.each do |column_name|
@@ -62,6 +77,7 @@ def remove_column(table_name, *column_names)
             remove_indexes(table_name, column_name)
             do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP COLUMN #{quote_column_name(column_name)}"
           end
+          clear_cache!
         end
 
         def change_column(table_name, column_name, type, options = {})
@@ -77,16 +93,19 @@ def change_column(table_name, column_name, type, options = {})
             sql_commands << "ALTER TABLE #{quote_table_name(table_name)} ADD CONSTRAINT #{default_constraint_name(table_name,column_name)} DEFAULT #{quote(options[:default])} FOR #{quote_column_name(column_name)}"
           end
           sql_commands.each { |c| do_execute(c) }
+          clear_cache!
         end
 
         def change_column_default(table_name, column_name, default)
           remove_default_constraint(table_name, column_name)
           do_execute "ALTER TABLE #{quote_table_name(table_name)} ADD CONSTRAINT #{default_constraint_name(table_name, column_name)} DEFAULT #{quote(default)} FOR #{quote_column_name(column_name)}"
+          clear_cache!
         end
 
         def rename_column(table_name, column_name, new_column_name)
           detect_column_for!(table_name,column_name)
           do_execute "EXEC sp_rename '#{table_name}.#{column_name}', '#{new_column_name}', 'COLUMN'"
+          clear_cache!
         end
 
         def remove_index!(table_name, index_name)
@@ -335,6 +354,7 @@ def views_real_column_name(table_name,column_name)
         # === SQLServer Specific (Column/View Caches) =================== #
 
         def initialize_sqlserver_caches
+          @sqlserver_columns_cache = {}
           @sqlserver_views_cache = nil
           @sqlserver_view_information_cache = {}
           @sqlserver_quoted_column_and_table_names = {}