More consistent API.

src/dodb/partition.cr

@@ -43,11 +43,10 @@ class DODB::Partition(V) < DODB::Indexer(V)
 	end
 
 	def get(partition) : Array(V)
-		r_value = Array(V).new
-
 		partition_directory = indexing_directory partition
+		raise MissingEntry.new(@name, partition) unless Dir.exists? partition_directory
 
-		return r_value unless Dir.exists? partition_directory
+		r_value = Array(V).new
 
 		Dir.each_child partition_directory do |child|
 			r_value << @storage[get_key child]

src/dodb/tags.cr

@@ -42,11 +42,10 @@ class DODB::Tags(V) < DODB::Indexer(V)
 	end
 
 	def get_with_indice(tag : String) : Array(Tuple(V, Int32))
-		r_value = Array(Tuple(V, Int32)).new
-
 		tag_directory = indexing_directory tag
+		raise MissingEntry.new(@name, tag) unless Dir.exists? tag_directory
 
-		return r_value unless Dir.exists? tag_directory
+		r_value = Array(Tuple(V, Int32)).new
 
 		Dir.each_child tag_directory do |child|
 			key = get_key child
@@ -56,10 +55,18 @@ class DODB::Tags(V) < DODB::Indexer(V)
 		r_value
 	end
 
+	# `get_with_indices` gets values with all the tags.
+
 	def get_with_indices(keys : Array(String)) : Array(Tuple(V, Int32))
 		r_value = Array(Tuple(V, Int32)).new
+		return r_value if keys.size < 1
+
+		first_key = keys.pop
+		r_value = get_with_indice(first_key) rescue return [] of Tuple(V, Int32)
+
 		keys.each do |tag|
-			r_value.concat get_with_indice tag
+			values = get_with_indice(tag) rescue return [] of Tuple(V, Int32)
+			r_value &= values
 		end
 		r_value
 	end