implement support for hash index

lib/solid_cache/store/api.rb

@@ -16,6 +16,7 @@ def delete_matched(matcher, options = {})
         instrument :delete_matched, matcher do
           raise ArgumentError, "Only strings are supported: #{matcher.inspect}" unless String === matcher
           raise ArgumentError, "Strings cannot start with wildcards" if SQL_WILDCARD_CHARS.include?(matcher[0])
+          raise NotImplementedError, "Primary Key uses a Hash Index, delete_matched method is not supported in this case" if primary_key_using_hash_index?
 
           options ||= {}
           batch_size = options.fetch(:batch_size, 1000)
@@ -49,6 +50,10 @@ def clear(options = nil)
       end
 
       private
+        def primary_key_using_hash_index?
+          ActiveRecord::Base.connection.indexes(:activesupport_cache_entries).first {|i| i.columns.first == 'key'}.using == :hash
+        end
+
         def read_entry(key, **options)
           deserialize_entry(read_serialized_entry(key, **options), **options)
         end

test/unit/delete_matched_test.rb

@@ -51,6 +51,13 @@ class DeleteMatchedTest < ActiveSupport::TestCase
     assert @cache.exist?(other_key)
   end
 
+  test "will raise error if hash index is used" do
+    # TODO: change migration to have hash index.
+    assert_raise NotImplementedError do
+      @cache.delete_matched("foo")
+    end
+  end
+
   test "fails when starts with %" do
     assert_raise ArgumentError do
       @cache.delete_matched("%foo")