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US 4,829,427 AGranted
Database query code generation and optimization based on the cost of alternate access methods
AssigneeData General Corporation
InventorNancy L. Green
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AssigneeData General Corporation
InventorNancy L. Green
Estimating the term…
An optimizer-code generator for use in a data base system. The optimizer-code generator employs a component called a scan analyzer for performing implementation-dependent analysis and providing implementation-dependent query code. The optimizer-code generator receives a query in logical tree form. It first optimizes the logical tree. In so doing, it provides information from the logical tree to the scan analyzer, which specifies what methods are available for accessing information required for the query and what each of the available methods costs. The optimizer-code generator uses the cost information in its optimization of the logical tree and specifies the access methods to be used in the logical tree. The code generator then uses the logical tree to generate query code. In so doing, it provides the specifications of the access methods to the scan analyzer, which returns query code for the access method. The code generator then incorporates the query code for the access method in the query code which it generates from the logical tree.
In a digital computer system employing a data base system for accessing stored data, means for transforming logical query data representing a query to be performed by said data base system into query code executable by said data base system comprising:
In a digital computer system employing a data base system for accessing stored data by means of a plurality of access methods, improved query code generation means for generating query code executable by said data base system from logical query data representing a query wherein the improvement comprises:
In a digital computer system employing a data base system for accessing stored data by means of a plurality of access methods, improved means for optimizing logical query data corresponding to queries comprising:
In a data base system implemented in a digital computer system, the method of transforming logical query data representing a query to be performed by said data base system into logical query data representing a more efficient form of said query comprising the steps of:
In a data base system implemented in a digital computer system, the method of transforming logical query data into query code executable by said data base system comprising the steps of:
Dependencies are inferred from the claim text.