Evaluation strategy for execution of SQL queries involving recur

Details Evaluation strategy for execution of SQL queries involving recur Evaluation strategy for execution of SQL queries involving recur

1995-02-17

1996-08-13

Kulik, Paul V.

Boots, shoes, and leggings

364DIG1, 3642821, 3642834, G06F 1730

Patent

active

055465706

ABSTRACT:
The present invention provides an evaluation strategy for the execution of SQL queries involving recursion and table queues in a relational database management system. The table queue is established for the query in the memory of the computer, and tuples are generated by tuple-producing operators in the query for storage into the table queue. As operators of the query read the stored tuples from the table queue, a first end-of-file condition, termed a Temporary End-Of-File, occurs when all of the tuples currently stored in the table queue have been retrieved and control is returned to the operator reading from the table queue. A retry request for additional tuples is generated by the operator through the table queue to the tuple-producing operators. If the tuple-producing operators can generate additional tuples, then these additional tuples are stored into the table queue and control is returned to the operator reading from the table queue in response to the retry request. If the tuple-producing operators cannot generate the additional tuples, then a second end-of-file condition, termed a Permanent End-Of-File, occurs and control is returned to the operator reading from the table queue.

REFERENCES:
Haas et al., "Extensible Query Processing in Starburst", IBM Almaden Research Center, San Jose, CA (US), ACM 1989, pp. 377-388.
Selinger et al, "Access Path Selection in a Relational Database Management System", IBM Research Division, San Jose, CA (US), ACM, 1979, pp. 23-34.
Lohman et al., "Research Report--Query Processing in R*", IBM Research Laboratory, San Jose, CA (US) IBM Research Division, Apr. 1984, pp. 1-33.
Lafortune et al., "A State Transition Model for Distributed Query Processing", University of California, ACM transactions on Database Systems, vol. 11, No. 3, Sep 1986 (294-322).

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