I was researching on cache replacement strategy as well. 2Q has one disadvantage see this exellent paper: http://www.almaden.ibm.com/cs/people/dmodha/#ARC see the paper "ARC: A Self-Tuning, Low Overhead Replacement Cache" for theory and "One Up on LRU" for implementation details. ARC requires no tuning and can switch fast between chaging patterns. Best of all is it is resistant to a "sequential scan" pattern. and i think it's even easier to implement then 2q :)
does pgbench test with relatively large sequential scans? ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match