schema cache already has the columns as a hash, so use that

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -287,7 +287,7 @@ def reset_sequence!(table, column, sequence = nil)
       # Inserts the given fixture into the table. Overridden in adapters that require
       # something beyond a simple insert (eg. Oracle).
       def insert_fixture(fixture, table_name)
-        columns = Hash[schema_cache.columns(table_name).map { |c| [c.name, c] }]
+        columns = schema_cache.columns_hash(table_name)
 
         key_list   = []
         value_list = fixture.map do |name, value|

activerecord/lib/active_record/connection_adapters/schema_cache.rb

 module ActiveRecord
   module ConnectionAdapters
     class SchemaCache
-      attr_reader :columns_hash, :primary_keys, :tables, :version
+      attr_reader :primary_keys, :tables, :version
       attr_accessor :connection
 
       def initialize(conn)
@@ -39,6 +39,16 @@ def columns(table = nil)
         end
       end
 
+      # Get the columns for a table as a hash, key is the column name
+      # value is the column object.
+      def columns_hash(table = nil)
+        if table
+          @columns_hash[table]
+        else
+          @columns_hash
+        end
+      end
+
       # Clears out internal caches
       def clear!
         @columns.clear