[postgis-devel] Re: [postgis-users] GIST index speed

[Paul Ramsey]

Mark,

Is it possible something terrible is happening in LWGEOM_gist_consistent?

The place the slow differs from the fast is that the slow spends a
great deal of time in _memcpy, which is driven by toast fetching,
which is driven by LWGEOM_gist_consistent.

There's lots of activity in the operating system, as well, in
vm_fault, which again reflects the idea that we are doing a lot of
memory allocation.

P.

On Mon, Jun 9, 2008 at 7:48 AM, Mark Cave-Ayland
<mark.cave-ayland at siriusit.co.uk> wrote:
> Paul Ramsey wrote:
>>
>> Bummer. Well if you need any other cock-eyed theories, let me know :)
>>
>> P
>
> Hi Paul,
>
> Please feel free to add more: I think it's that we're doing something
> strange with palloc/pfree/TOAST, maybe casting, or it's something in the
> PostgreSQL index AM. Do you have any success with profiling under OS X? If
> so, it would be good to get at least a working profile output of both query
> cases, so we can try and determine where the time is being swallowed during
> the index scan.
>
>
> ATB,
>
> Mark.
>
> --
> Mark Cave-Ayland
> Sirius Corporation - The Open Source Experts
> http://www.siriusit.co.uk
> T: +44 870 608 0063
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