[postgis-devel] Calling Index Genii

[Paul Ramsey]

And I just did turn on logging and hey presto, both indexes take about
the same number of tree traversals to generate the result. So the
trees are more-or-less the same shape. So... what's left? I'll post
the shark results to see if anything jumps out at you Mark, doesn't
jump out at me. At this point the only thing I've got left is using a
varlena key in the new index and a fixed length one in the old one.

P.

On Fri, Dec 31, 2010 at 3:15 PM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> Actually first I need to just turn on logging and count the number of calls to gist consistent. If my guess about the bad tree is right, I should see about five times as many calls on the new index. If the number of calls is in the same order of magnitude, suspicion shifts to the varlena key and associated overhead (which I find hard to believe).
>
> I have already run it through the shark and it is not very useful... At least the functions it points to don't scream, hey! Look at my huge overhead!
>
> P.
>
> On 2010-12-31, at 4:11 AM, Mark Cave-Ayland <mark.cave-ayland at siriusit.co.uk> wrote:
>
>> On 31/12/10 06:15, Paul Ramsey wrote:
>>
>>> Actually, testing again on the laptop (apples to apples) the speed
>>> different with 2D data is down to 3ms-on-new vs 1ms-on-old. When
>>> pulling a much larger result set (2000 records) the speed difference
>>> is 10ms-on-new vs 6ms-on-old. So it's closer, but still not
>>> equivalent.
>>>
>>> P.
>>
>> Sounds like it's time to build a profileable version of the library. Can you build with CFLAGS="-O0 -pg" and then use your favourite profiling tool (gprof/Shark) to see the differences in where the time is being spent?
>>
>>
>> ATB,
>>
>> Mark.
>>
>> --
>> Mark Cave-Ayland - Senior Technical Architect
>> PostgreSQL - PostGIS
>> Sirius Corporation plc - control through freedom
>> http://www.siriusit.co.uk
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>>
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>