1 files changed, 64 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/table_metadata.rb b/activerecord/lib/active_record/table_metadata.rb
new file mode 100644
index 0000000000..f9bb1cf5e0
--- /dev/null
+++ b/activerecord/lib/active_record/table_metadata.rb
@@ -0,0 +1,64 @@
+module ActiveRecord
+  class TableMetadata # :nodoc:
+    delegate :foreign_type, :foreign_key, to: :association, prefix: true
+    delegate :association_primary_key, to: :association
+
+    def initialize(klass, arel_table, association = nil)
+      @klass = klass
+      @arel_table = arel_table
+      @association = association
+    end
+
+    def resolve_column_aliases(hash)
+      # This method is a hot spot, so for now, use Hash[] to dup the hash.
+      #   https://bugs.ruby-lang.org/issues/7166
+      new_hash = Hash[hash]
+      hash.each do |key, _|
+        if (key.is_a?(Symbol)) && klass.attribute_alias?(key)
+          new_hash[klass.attribute_alias(key)] = new_hash.delete(key)
+        end
+      end
+      new_hash
+    end
+
+    def arel_attribute(column_name)
+      arel_table[column_name]
+    end
+
+    def type(column_name)
+      if klass
+        klass.type_for_attribute(column_name.to_s)
+      else
+        Type::Value.new
+      end
+    end
+
+    def associated_with?(association_name)
+      klass && klass._reflect_on_association(association_name)
+    end
+
+    def associated_table(table_name)
+      return self if table_name == arel_table.name
+
+      association = klass._reflect_on_association(table_name)
+      if association && !association.polymorphic?
+        association_klass = association.klass
+        arel_table = association_klass.arel_table.alias(table_name)
+      else
+        type_caster = TypeCaster::Connection.new(klass, table_name)
+        association_klass = nil
+        arel_table = Arel::Table.new(table_name, type_caster: type_caster)
+      end
+
+      TableMetadata.new(association_klass, arel_table, association)
+    end
+
+    def polymorphic_association?
+      association && association.polymorphic?
+    end
+
+    protected
+
+    attr_reader :klass, :arel_table, :association
+  end
+end