Browse Prior Art Database

Deductive Index Scan Suppression

IP.com Disclosure Number: IPCOM000051829D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Aubertin, EE: AUTHOR [+2]

Abstract

A current implementation of random file additions in a computer system involves searching the file's index to produce a ""no record found'' (NRF) condition and then searching that index again to ensure that the item to be added is not a duplicate.

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Deductive Index Scan Suppression

A current implementation of random file additions in a computer system involves searching the file's index to produce a ""no record found'' (NRF) condition and then searching that index again to ensure that the item to be added is not a duplicate.

A typical file access sequence during execution of an application program (Fig. 1) is: . attempt to retrieve a record by a given key, . receive a no record found indication, and . issue an ""add'' operation.

When the addition (Fig. 2) is performed, it is possible that: . the same record had been added, or . the key of the record to be added is different than the key which caused the ""no record found'' condition.

Therefore, when the following conditions are met, the duplicate search is obviated: . The operation preceding the addition was an input operation (Fig. 3) producing ""no record found'' condition. . The key of the added record is the same as that used for the input operation. . No additions have been made to the file since the ""no record found'' condition was detected.

Whenever an input operation (Fig. 3) is issued, the search key and the current end-of-file location are saved for that logical access path. Anytime an addition operation (Fig. 2) is performed, the physical end-of-file location is modified. Thus, the information for determining whether to suppress the duplicate search is readily available.

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