Warm cache costing: a feedback optimization technique for buffer pool aware costing

Most modern RDBMS depend on the query processing optimizer’s cost model to choose the best execution plan for a given query. Since the physical IO (PIO) is a costly operation to execute, it naturally has an important weight in RDBMS classical cost models, which assume that the data is disk-resident and does not fit in the available main memory. However, this assumption is no longer true with the advent of cheap large main memories. In this paper, we discuss the importance of considering the buffercache occupancy during optimization and propose the Warm Cache Costing (WCC) model as a new technique for buffer-pool aware query optimization. The WCC-model is a novel feedback optimization technique, based on the execution statistics by learning PIOcompensation (PIOC) factors. The PIOC factor defines the average percentage of a table which is cached in the buffer pool. These PIOC factors are used in subsequent query optimizations to better estimate the PIO, thus leading to better plans....

• Type: Conference
• Year: 2010
• Where: EDBT
• Authors: H. S. Ramanujam, Edwin Seputis
• Keywords: Database, EDBT 2010, Feedback Optimization, Query Optimizations, Query Processing