SCHEMA MAPPING SYSTEM AND METHOD

A schema mapping system and method are particularly suitable for expressing a schema mapping between two database schemas that may be heterogeneous (restructuring views of each other). The schema mapping system is useful for generating a least cost query plan expressible on a plurality of heterogeneous tables that are restructuring views of each other. The system may be configured to receive a query against one of the tables and convert it to a plurality of alternate queries, each formatted for the particular schema of a different one of the plurality of heterogeneous tables. In generating the alternate queries, the schema mapping system may utilize SchemaSQL view definitions and may employ restructuring operators expressing and capable of conducting a restructuring of a table into a restructuring view of the table. The system may employ a canonical schema and a virtual canonical table to express a mapping between restructuring views, and may utilize the schema mapping for purposes of query conversion. The alternate queries may be costed and optimized and a query plan returned that has a least cost or service time involved.