pgsql/contrib/pgbench README.pgbench README.pg ...

Hi Tatsuo,

I've attached a patch for the version of pgbench in CVS. It includes the
following changes:

- fix some spelling mistakes, indentation stuff, etc.

- minor code cleanup -- (void) args instead of (), etc.

- allocate the state array dynamically, so that it is only as
large as needed. This reduces the memory consumption of pgbench
slightly, and makes a larger MAXCLIENTS setting possible

- (the only controversial change) add an option "-l" to log
transaction latencies to a file. The "transaction latency"
is the time between when the BEGIN is issued and the transaction
commits. This is written to a file, along with the client #
and the transaction #. The data in the file can then be used
for things like:

- consistency analysis: is the TPS the same through the
entire run of pgbench, or does it change?

- more detailed stats: what is the average latency, worse-case
latency, best-case latency?

- graphs: feed the data to gnuplot, graph latency versus. time

- etc.

I was going to store this data in memory and write it to disk
at the end of the pgbench run, but that isn't feasible because
the data can be very large: for example, ~70MB if benchmarking
128 clients doing 100,000 transactions each.

Cheers,

Neil