An eddy [2] is a highly adaptive query processing operator that continuously reoptimizes a query in response to changing runtime conditions. It does this by treating query processing as routing of tuples through operators and making per-tuple routing decisions. The benefits of such adaptivity can be significant, especially in highly dynamic environments such as data streams, sensor query processing, web querying, etc. Various parties have asserted that the cost of making per-tuple routing decisions is prohibitive. We have implemented eddies in the PostgreSQL open source database system [1] in the context of the TelegraphCQ project. In this paper, we present an "apples-to-apples" comparison of PostgreSQL query processing overhead with and without eddies. Our results show that with some minor tuning, the overhead of the eddy mechanism is negligible.
For example, in REF , the adaptive decisions are revised after a batch of tuples has been processed so that the cost of making routing decisions can be effectively amortized.
An initial study of overheads of eddies
SGMD
Computer Science