Re: [HACKERS] Re: v7.1b4 bad performance

Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
>> It seems to me that the branches table should have at least 10 to 100
>> entries, and tellers about 10 times whatever branches is. 100000
>> accounts rows seems enough though.

> Those numbers are defined in the TPC-B spec.

Ah. And of course, the TPC bunch never thought anyone would be
interested in the results with scale factors so tiny as one ;-),
so they didn't see any problem with it.

Okay, plan B then: let's ask people to redo their benchmarks with
-s bigger than one. Now, how much bigger?

To the extent that you think this is a model of a real bank, it should
be obvious that the number of concurrent transactions cannot exceed the
number of tellers; there should never be any write contention on a
teller's table row, because only that teller (client) should be issuing
transactions against it. Contention on a branch's row is realistic,
but not from more clients than there are tellers in the branch.

As a rule of thumb, then, we could say that the benchmark's results are
not to be believed for numbers of clients exceeding perhaps 5 times the
scale factor, ie, half the number of teller rows (so that it's not too
likely we will have contention on a teller row).

regards, tom lane