Query execution engine; Query engine; Relational query processor
The query processor in a database management system receives as input a query request in the form of SQL text, parses it, generates an execution plan, and completes the processing by executing the plan and returning the results to the client.
In a relational database system the query processor is the module responsible for executing database queries. The query processor receives as input queries in the form of SQL text, parses and optimizes them, and completes their execution by employing specific data access methods and database operator implementations. The query processor communicates with the storage engine, which reads and writes data from the disk, manages records, controls concurrency, and maintains log files.
Typically, a query processor consists of four sub-components; each of them corresponds to a different stage in the lifecycle of a query. The sub-components are the query parser,...
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