[HACKERS] Estimation of HashJoin Cost

2012-11-01 Thread Qi Huang
Hi, Dear HackersI 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

Re: [HACKERS] Estimation of HashJoin Cost

2012-11-01 Thread Kevin Grittner
Qi Huang wrote: I need to estimate the hashjoin cost in my research. 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?