| 摘要 |
A method and apparatus, and article of manufacture are provided to process an abstract query of a database abstraction constructed over an underlying physical data storage mechanism. The database may comprise a single data source, or a federated source spanning multiple systems. Embodiments of the invention process an abstract query by generating an intermediate representation of the abstract query. In one embodiment, the intermediate representation comprises an abstract query plan. An abstract query plan includes a combination of elements from the data abstraction model and elements relating to the underlying physical data storage mechanism. Once generated, a back-end component may easily traverse the abstract query plan to generate an SQL statement (or other resolved query) corresponding to the abstract query. Further, once constructed, the abstract query plan provides a platform for many different optimizations that may be selected by a user or by the runtime component inspecting the abstract query plan prior to creating the resolved query.
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