Managing Query Compilation Memory Consumption to Improve DBMS Throughput
  While there are known performance trade-offs between database page buffer pool and query execution memory allocation policies, little has been written on the impact of query compilation memory use on overall throughput of the database management system (DBMS). We present a new aspect of the query optimization problem and offer a solution implemented in Microsoft SQL Server 2005. The solution provides stable throughput for a range of workloads even when memory requests outstrip the ability of the hardware to service those requests. 
Boris Baryshnikov, Cipri Clinciu, Conor Cunningham, Leo Giakoumakis,   Slava Oks, Stefano Stefani