Hi, Dear Hackers I need to estimate the hashjoin cost in my research. As the
textbook shows, it is 3(R+S) where R and S are the size of the tablesize of the
two tables, which realistically only considers the cost of IO. But this is
obviously too theoretical. What is the correct way to estimate the cost of
hashjoin? I looked at the code of final_cost_hashjoin() . It is not clear what
factor it is considering. So, except the I/O to and from disk, what other
factors are affecting the cost of hahsjoin? Also, is there any way to force
postgres abide on the estimation of Hashjoin cost as 3(R+S), which also means,
to make hashjoin cost mainly spend on I/O?
Thanks
Best RegardsHuang Qi VictorComputer Science of National University of Singapore
