Described herein are instance mapping techniques that facilitate the rewrite of queries to access materialized views that have multiple instances of the same table. Instance mapping techniques are processes for determining a mapping between equivalent instances in a query and materialized view definition. An instance in a query that is equivalent to an instance in a materialized view definition (or another query) is treated as if they are identical labels for the same table for the purposes of rewriting a query. To determine the mapping between instances of a table in a query and a materialized view definition, join predicates in the query and materialized view definition that involve instances of the table are compared.