QUERY HANDLING IN DATABASES WITH REPLICATED DATA

摘要

The same data is stored in at least two different database management systems (DBMS's), including a columnar DBMS (320.2) and a non-columnar (e.g. row-oriented) DBMS (320.1). The columnar DBMS may provide fast responses to queries involving aggregation, and such queries can be routed to the columnar DBMS. A query may be routed to the non-columnar DBMS if for example the query execution involves only small DBMS tables on the non-columnar DBMS. In some situations, an execution time estimate can be obtained from each DBMS, and the query is routed to the DBMS providing the shortest estimate.