Defaults hash can go on the model

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -2,7 +2,6 @@ module ActiveRecord
   module ConnectionAdapters
     class SchemaCache
       attr_reader :columns, :columns_hash, :primary_keys, :tables
-      attr_reader :column_defaults
       attr_reader :connection
 
       def initialize(conn)
@@ -19,12 +18,6 @@ def initialize(conn)
           }]
         end
 
-        @column_defaults = Hash.new do |h, table_name|
-          h[table_name] = Hash[columns[table_name].map { |col|
-            [col.name, col.default]
-          }]
-        end
-
         @primary_keys = Hash.new do |h, table_name|
           h[table_name] = table_exists?(table_name) ?
                           conn.primary_key(table_name) : 'id'
@@ -38,15 +31,10 @@ def table_exists?(name)
         @tables[name] = connection.table_exists?(name)
       end
 
-      # Clears out internal caches:
-      #
-      #   * columns
-      #   * columns_hash
-      #   * tables
+      # Clears out internal caches
       def clear!
         @columns.clear
         @columns_hash.clear
-        @column_defaults.clear
         @tables.clear
       end
 
@@ -54,7 +42,6 @@ def clear!
       def clear_table_cache!(table_name)
         @columns.delete table_name
         @columns_hash.delete table_name
-        @column_defaults.delete table_name
         @primary_keys.delete table_name
         @tables.delete table_name
       end

activerecord/lib/active_record/model_schema.rb

@@ -236,7 +236,7 @@ def columns_hash
       # Returns a hash where the keys are column names and the values are
       # default values when instantiating the AR object for this table.
       def column_defaults
-        @column_defaults ||= connection.schema_cache.column_defaults[table_name]
+        @column_defaults ||= Hash[columns.map { |c| [c.name, c.default] }]
       end
 
       # Returns an array of column names as strings.