Обсуждение: hacking postgres hashjoin algorithm
Hello there I am trying to play around with the hashjoin algorithm in postgres. I am using the statement like Select count(*) from r,s where r.id=s.id; I looked at the function ExecHashJoin() in nodeHashjoin.c and cannot find where the algorithm is comparing if r.id equals s.id please advise. Regards hal
On Sun, Oct 15, 2006 at 11:08:18PM -0400, HS wrote: > Hello there > > I am trying to play around with the hashjoin algorithm in postgres. > > I am using the statement like > Select count(*) from r,s where r.id=s.id; > > I looked at the function ExecHashJoin() in nodeHashjoin.c and cannot > find where the algorithm is comparing if r.id equals s.id The code doing the work is actually ExecScanHashBucket() which is in nodeHash.c. The actual check is done by the ExecQual there... Hope this helps, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
from my understanding, postgres first needs to partition the tables. ExecHashTableCreate() is the function that partitions the tables right? Martijn van Oosterhout wrote: > On Sun, Oct 15, 2006 at 11:08:18PM -0400, HS wrote: >> Hello there >> >> I am trying to play around with the hashjoin algorithm in postgres. >> >> I am using the statement like >> Select count(*) from r,s where r.id=s.id; >> >> I looked at the function ExecHashJoin() in nodeHashjoin.c and cannot >> find where the algorithm is comparing if r.id equals s.id > > The code doing the work is actually ExecScanHashBucket() which is in > nodeHash.c. The actual check is done by the ExecQual there... > > Hope this helps,