Identifying robust plans through plan diagram reduction

Estimates of predicate selectivities by database query optimizers often differ significantly from those actually encountered during query execution, leading to poor plan choices and inflated response times. In this paper, we investigate mitigating this problem by replacing selectivity error-sensitive plan choices with alternative plans that provide robust performance. Our approach is based on the recent observation that even the complex and dense "plan diagrams" associated with industrial-strength optimizers can be efficiently reduced to "anorexic" equivalents featuring only a few plans, without materially impacting query processing quality. Extensive experimentation with a rich set of TPC-H and TPCDS-based query templates in a variety of database environments indicate that plan diagram reduction typically retains plans that are substantially resistant to selectivity errors on the base relations. However, it can sometimes also be severely counter-productive, with t...

• Type: Journal
• Year: 2008
• Where: PVLDB
• Authors: Harish D., Pooja N. Darera, Jayant R. Haritsa
• Keywords: Database Query Optimizers, PVLDB 2008, Query Execution, Selectivity Error-sensitive Plan