On Mon, 2005-06-20 at 17:09 -0400, Alvaro Herrera wrote:
> On Mon, Jun 20, 2005 at 09:55:12PM +0100, Simon Riggs wrote:
>
> > I put those changes in mainly for COPY. If you don't make any request at
> > all to FSM then a relation never gets to the MRU relation FSM list. I
> > agree that it is not strictly necessary, but leaving it off would be a
> > change in behaviour, since COPY did previously cause the relation to get
> > to the MRU. That could be a problem, since a relation might not then be
> > allocated any FSM pages following a vacuum.
>
> Is that a problem?
Not for me, but I wanted to explain the change in behaviour that
implies.
> If the pages don't fit in FSM, then maybe the system
> is misconfigured anyway. The person running the DW should just increase
> the FSM settings, which is hardly a costly thing because it uses so
> little memory.
If you aren't on the relation list you don't get any more pages than the
minimum. No matter how many fsm_pages you allocate. If fsm_pages covers
everything, then you are right, there is no problem.
Best Regards, Simon Riggs
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
