Re: Simulating Clog Contention

On Thu, Jan 12, 2012 at 4:31 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> The following patch adds a pgbench option -I to load data using
> INSERTs, so that we can begin benchmark testing with rows that have
> large numbers of distinct un-hinted transaction ids. With a database
> pre-created using this we will be better able to simulate and thus
> more easily measure clog contention. Note that current clog has space
> for 1 million xids, so a scale factor of greater than 10 is required
> to really stress the clog.

Running with this patch with a non-default scale factor generates the
spurious notice:

"Scale option ignored, using pgbench_branches table count = 10"

In fact the scale option is not being ignored, because it was used to
initialize the pgbench_branches table count earlier in this same
invocation.

I think that even in normal (non-initialization) usage, this message
should be suppressed when the provided scale factor
is equal to the pgbench_branches table count.

Cheers,

Jeff