Application of Micro-specialization to Query Evaluation Operators

Relational database management systems support a wide variety of data types and operations. Such generality involves much branch condition checking, which introduces inefficiency within the query evaluation loop. We previously introduced micro-specialization, which improves performance by eliminating unnecessary branching statements and the actual code branches by exploiting invariants present during the query evaluation loop. In this paper, we show how to more aggressively apply micro-specialization to each individual operator within a query plan. Rather than interpreting the query plan, the DBMS dynamically rewrites its object code to produce executable code tailored to the particular query. We explore opportunities for applying micro-specialization to DBMSes, focusing on query evaluation. We show through an examination of program execution profiles that even with a simple query in which just a few operators are micro-specialized, significant performance improvement can be achieved.