Re: Priorities for users or queries?

Magnus Hagander wrote:
> Most likely, you do not want to do this. You *can* do it, but you are
> quite likely to suffer from priority inversion

Papers I've read suggest that the benefits of priorities
vastly outweigh the penalties of priority inversion for
virtually all workloads on most all RDBMs's including
PostgreSQL.

This CMU paper in particular tested PostgreSQL (and DB2)
on TPC-C and TPC-W workloads and found that indirectly
influencing I/O scheduling through CPU priorities
is a big win for postgresql.

http://www.cs.cmu.edu/~bianca/icde04.pdf

"For TPC-C running on PostgreSQL,
the simplest CPU scheduling policy (CPU-Prio) provides
a factor of 2 improvement for high-priority transactions,
while adding priority inheritance (CPU-Prio-Inherit)
provides a factor of 6 improvement while hardly
penalizing low-priority transactions."

Have you heard of any workload on any RDBMS where priority inversion
causes more harm than benefit?

Ron Mayer