Re: Fw: Informix thread management

----- Original Message -----
From: "Andy Kent" <andykent.bristol@virgin.net>
To: <informix-list@iiug.org>
Sent: Thursday, January 08, 2004 3:18 AM
Subject: Re: Fw: Informix thread management


> > > Kind of an intuitive thing with X-tree. You see it running merrily
along
> > > with the speedometer needles pegged at whatever their rate is - and
then
> > > suddenly they drop off to zero for 10-20-30 (or whatnot) seconds - you
> > know
> > > something else is happening, but it's not happening with your query.
>
> Is there any *proper* documentation for xtree anywhere? It's pretty
> hit-and-miss trying to work out which table it's scanning.

Performance guide.

>
> The query I'm trying to analyse *looks* as though it's spending all
> its time repeatedly filtering on the results of a subquery. It only
> seems to have allocated one thread to this, so I am getting zero
> benefit from throwing masses of PDQ and DS resources at it. The weird
> thing is the subquery is uncorrelated, so I'd expect the engine just
> to run it the once, do an autoindex on the resultant TT and then do
> indexes lookups to the TT. Why would it be spending all its time on
> the filter to the subquery?

Filters take no time at all, sounds like a nested loop for which Parallelism
and DS memory would not help. Send me the schema of the tables involved and
the rowcounts and maybe I can shed some light on it.

>
> But of course in the absence of any decent xtree documentation,
> there's an element of guesswork in the above.
>
> We're on 7.31.UC5.
>
> Thanks
>
> Andy
>


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