[postgis-devel] Calling Index Genii

[Nicklas Avén]

great

.. or not so great, would have been more way that way I guess ...



2011-01-05 skrev 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 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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>>>>
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