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METHOD FOR EFFICIENT BACKEND EVALUATION OF AGGREGATES ON COMPOSITE RELATIONSHIPS IN A RELATIONALLY MAPPED ER MODEL
METHOD FOR EFFICIENT BACKEND EVALUATION OF AGGREGATES ON COMPOSITE RELATIONSHIPS IN A RELATIONALLY MAPPED ER MODEL
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机译:关联ER模型中复合关联的骨料有效后端评价方法。
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摘要
A computer-implemented method is disclosed for executing aggregate queries of composite relationships from an Entity-Relationship (ER) model which sources data from a plurality of heterogeneous and decentralised databases. The method comprises maintaining an ER model comprising a plurality of entities En for which data exists in one or more databases, and one or more relationships rn between those entities. An aggregate query is received relating to a composite relationship cr(r1, r2) involving entities E1, E2 and E3 wherein r1 is a relation between E1 and E2, and wherein r2 is a relation between E2 and E3. The computation of the aggregate query is optimized by selecting an aggregation strategy according to the relation between entities E1, E2 and E3, such that a single table aggregation strategy, a semi-join strategy or a join strategy is selected according to the relation between tables defining entities in the ER model.
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机译:公开了一种计算机实现的方法,用于从实体关系(ER)模型执行复合关系的聚合查询,该实体关系模型从多个异构和分散的数据库中获取数据。该方法包括维持一个ER模型,该ER模型包括多个实体E n Sub>,其数据存在于一个或多个数据库中,以及这些实体之间的一个或多个关系r n Sub>。接收到涉及涉及实体E1,E2和E3的复合关系cr(r1,r2)的汇总查询,其中r1是E1和E2之间的关系,其中r2是E2和E3之间的关系。通过根据实体E1,E2和E3之间的关系选择聚合策略来优化聚合查询的计算,从而根据表之间的关系选择单表聚合策略,半联接策略或联接策略在ER模型中定义实体。
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