A Cost Model for a Fingered Join Operator in Relational Query Plans

SQL;Query Optimization;Join;Databases;Finger;Computer Science

Prathish, Vishnu

University of Waterloo

关键词: SQL;    Query Optimization;    Join;    Databases;    Finger;    Computer Science;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/9521/5/Prathish_Vishnu.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

We introduce the finger aware cursor operator for relational join queries. It scans a list oftuples in a finger enabled manner when a nested loop join operation is performed. Usingthis scan operation, we improve the performance of nested loop join when compared towhen compared to conventional scan. To quantify the improvement in performance usingfingered scan, a statistic named runs that quantifies the degree of randomness in a listof records is introduced. This statistic is vital in assessing the performance improvementachieved using fingered scan. Using runs statistic as a key ingredient, we develop a costmodel that can assign a cost value to the join operation based on underlying fingeredscan. We then develop a cost formula and evaluate the cost model against a simulateddata set. We show that conventional System R cost model is not sufficient to capture theperformance improvement. We then evaluate using the new cost formula and show that itpredicts the cost of join operation correctly.