review fixes

- restore arel_table reset
- changelog was wrong
- always instantiate find_by_statement_cache
  - the inherited_hook is no longer useful for instantiating because
    contexts may not have been created yet, but it is still useful for
    resetting statement caches for contexts that _have_ been created
- column_for_attribute can stay on ModelSchema

Author: skipkayhil

activerecord/CHANGELOG.md

@@ -3,7 +3,7 @@
 
     Previously, models cached many adapter specific values which would prevent
     making queries against different database types. Now, those caches are per
-    `schema-context`, which can be configured in `database.yml`:
+    `schema_context`, which can be configured in `database.yml`:
 
     ```yaml
     primary:

activerecord/lib/active_record/model_schema.rb

@@ -493,7 +493,10 @@ def _returning_columns_for_insert(connection) # :nodoc:
       #   person.column_for_attribute(:nothing)
       #   # => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>
       def column_for_attribute(name)
-        model_schema.column_for_attribute(name)
+        name = name.to_s
+        columns_hash.fetch(name) do
+          ConnectionAdapters::NullColumn.new(name)
+        end
       end
 
       # Returns a hash where the keys are column names and the values are
@@ -586,6 +589,7 @@ def initialize_load_schema_monitor
 
         def reload_schema_from_cache(recursive = true)
           @any_schema_loaded = false
+          @arel_table = nil
           @attribute_names = nil
 
           # Reset all Schema instances

activerecord/lib/active_record/model_schema/schema.rb

@@ -25,7 +25,7 @@ def initialize(model_class, context_key)
         @attributes_builder = nil
         @column_defaults = nil
         @_returning_columns_for_insert = nil
-        @find_by_statement_cache = nil
+        initialize_find_by_cache
         @content_columns = nil
         @symbol_column_to_string_name_hash = nil
       end
@@ -118,14 +118,6 @@ def symbol_column_to_string(name_symbol)
         @symbol_column_to_string_name_hash[name_symbol]
       end
 
-      # Returns the column object for a named attribute
-      def column_for_attribute(name)
-        name = name.to_s
-        columns_hash.fetch(name) do
-          ConnectionAdapters::NullColumn.new(name)
-        end
-      end
-
       # Reset all cached schema state
       def reload_schema_from_cache
         @_returning_columns_for_insert = nil
@@ -142,7 +134,6 @@ def reload_schema_from_cache
       end
 
       def cached_find_by_statement(connection, key, &block)
-        @find_by_statement_cache ||= { true => Concurrent::Map.new, false => Concurrent::Map.new }
         cache = @find_by_statement_cache[connection.prepared_statements]
         cache.compute_if_absent(key) { StatementCache.create(connection, &block) }
       end