[postgis-devel] Calling Index Genii

[Paul Ramsey]

Yes, sure. And now that I've counted the tree traversal that makes me
even more sure.

P

On Wed, Jan 5, 2011 at 7:33 AM, Nicklas Avén <nicklas.aven at jordogskog.no> wrote:
> Hi Paul
>
> Sorry for repeating myself, but are you sure you don't have a 3d index after
> all, even if you input 2d geometries. From some
> "add-empty-z-value-mechanism"?
>
> just curious
>
> /Nicklas
>
> 2011-01-05 skrev 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 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 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
>>>> t: +44 870 608 0063
>>>>
>>>> Sirius Labs: http://www.siriusit.co.uk/labs
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