Re: proposal for smaller indexes on index-ordered tables

On Tue, Jun 24, 2008 at 3:08 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> > Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> Now, *why* it is a mistake is interesting to speculate about, but
> >> let's confirm the theory first.
>
> > Could this be related to hint bit rewrites during indexing?
>
> If so, changing maintenance_work_mem won't improve the situation.
>
> What I personally suspect is that Jeff's index build is swapping like
> crazy, or else there's just some problem in the sort code for such a
> large sort arena. But let's get some evidence about how the index build
> time varies with maintenance_work_mem before jumping to conclusions.

Well it definitely isn't that, because the machine doesn't even have a swap
area defined. vmstat during the table creation and index creation look
really quite different. During the table sort there's a heavy r/w traffic
12-20MB/s, during the index creation it's lower. But seem to be CPU limited
(i.e. one CPU is maxed out the whole time, and iowait is not very high).

I guess nobody has any interest in my proposal, only in the departure of my
described experience from expected behavior :-(