+/**
+ * \brief Delete all tuples matching to the query.
+ * \returns all deleted tuples.
+ */
+extern vector *relation_delete(relation *r,tuple *query);
+
+/**
+ * \brief Return next tuple matching the query at or after the index.
+ * \returns any such matching tuple and updates *index to its index.
+ */
+extern void *relation_next(relation *r,vector_index *index,tuple *query);
+