Support changing indices for query

lib/chewy/search/query_proxy.rb

@@ -252,6 +252,15 @@ def initialize(parameter_name, request)
       def minimum_should_match(value)
         @request.send(:modify, @parameter_name) { minimum_should_match(value) }
       end
+
+      # Executes {Chewy::Search::Request#index} in the scope of newly created
+      # request object.
+      # @see Chewy::Search::Request#index
+      # @param indicies [Array<String>]
+      # @return [Chewy::Search::Request]
+      def index(*indices)
+        @request.index(*indices)
+      end
     end
   end
 end

lib/chewy/search/request.rb

@@ -773,6 +773,13 @@ def except(*values)
         chain { parameters.except!(values.flatten(1)) }
       end
 
+      # Returns a list of indexes to fetch.
+      # @param indices [Array<String>]
+      # @return [Chewy::Search::Request] new scope
+      def index(*indices)
+        chain { (@indices ||= []).concat(indices.flatten) }
+      end
+
       # @!group Additional actions
 
       # Returns total count of hits for the request. If the request
@@ -973,7 +980,7 @@ def raw_offset_value
       end
 
       def index_names
-        @index_names ||= _indexes.map(&:index_name).uniq
+        @index_names ||= @indices ? @indices.uniq : _indexes.map(&:index_name).uniq
       end
 
       def type_names