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.

主权项

1. A database access method comprising:
(1) receiving a database query relating to data which is stored in each of a first database and a second database, wherein the first database and the second database are two separate and discrete databases, wherein the first database is managed by a first database management system that includes a first query processor configured to execute queries directed to the first database, wherein the second database is managed by a second database management system that is distinct from the first database management system, the second database management system including a second query processor configured to execute queries directed to the second database, wherein at least one attribute of the data stored in the first database is stored in columnar form, and wherein none of the attributes of the data stored in the second database are stored in columnar form; (2) determining, externally from each of the first database management system and the second database management system, if the database query is to be executed on the first database or the second database based on the processing required by the database query and the form in which data is stored by the first and second database management systems, the determining comprising, checking if the database query involves computation of an aggregation and determining that the database query is to be executed on the first database responsive to the database query involving computation of an aggregation; and (3) providing the database query to the first query processor or the second query processor based on the determination made in operation (2).