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Efficient inter-task queue protocol

  • US 6,341,302 B1
  • Filed: 09/24/1998
  • Issued: 01/22/2002
  • Est. Priority Date: 09/24/1998
  • Status: Expired due to Fees
First Claim
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1. A system for executing database queries, comprising:

  • a set of task data structures representing a directed graph of logically interconnected tasks, the directed graph of logically interconnected representing an execution plan for executing at least a portion of a specified database query;

    an executor module for executing the tasks represented by the set of task data structures;

    a pair of queues for each pair of interconnected tasks represented by the set of task data structures, one of the queues in each pair comprising a down queue for sending requests from a parent task, comprising a first one of the pair of tasks, to a child task, comprising a second one of the pair of tasks, and the other of the queues in each pair for comprising an up queue for sending replies from the child task to the parent task, each reply corresponding to one of the requests;

    each of a first subset of the tasks including means for reading requests from a down queue in a respective one of the pairs of queues, for generating a corresponding result and for writing the result as a reply into the up queue in the respective pair of queues;

    each of a second subset of the tasks including means for writing requests into a down queue in a respective one of the pairs of queues, for reading a corresponding reply in the up queue in the respective pair of queues;

    wherein each task includes queue fullness checking means for checking that a first respective one of the queues is not full before writing data into the first respective queue, and queue empty checking means for checking that a second respective one of the queues is not empty before reading data from the second respective queue; and

    each task writes and reads data to and from respective ones of the queues without first acquiring ownership of a corresponding synchronization mechanism.

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