<p>A key estimator estimates the number of keys over a key range defined by key endpoints in an index to a data space. The number of keys in the key range required to be processed for a particular operation is estimated as a function of the number of pages referenced during a range level limited search. Two keys defining range endpoint keys are searched down to their lowest level in the tree. The level limit is then calculated as a function of desired granularity or accuracy of the estimate. The entire range of keys in the desired key range is then searched down to the level limit and the number of pages referenced during the search is counted and multiplied by an average key density per page to calculate the number of keys in the range.</p>
申请公布号
EP0252234(B1)
申请公布日期
1994.01.12
申请号
EP19870106180
申请日期
1987.04.28
申请人
INTERNATIONAL BUSINESS MACHINES CORPORATION
发明人
ANDERSON, MARK, JOHN;COLE, RICHARD LEE;DAVIDSON, WILLIAM, SIMPSON;YOUNGREN, LARRY WILLIAM;LEE, WILSON DOUGLAS;PASSE, PETER BERNARD;RICARD, GARY ROSS