On 29/06/10 05:36, Josh Berkus wrote:
>
> Having tinkered with it, I'll tell you that (2) is actually a very
> hard problem, so any solution we implement should delay as long as
> possible in implementing (2). In the case of Greenplum, what Mark did
> originally IIRC was to check against the global memory pool for each
> work_mem allocation. This often resulted in 100's of global locking
> checks per query ... like I said, feasible for DW, not for OLTP.
Actually only 1 lock check per query, but certainly extra processing and
data structures to maintain the pool information... so, yes certainly
much more suitable for DW (AFAIK we never attempted to measure the
additional overhead for non DW workload).
Cheers
Mark