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<body>Paul<br />
<br />
yes, it seemed like a great theory. are you sure it is not building a 3d index anyway. <br />
can you confirm that the "DIMENSIONALITY<br />
DETERMINED BY THE DATA" thing is working. Is there no mechanism somewhere that adds an empty z coordinate like get_3d_point (or whatever the name is) is doing.<br />
<br />
/Nicklas<br />
<br />
<br />
2010-12-31 skrev Paul Ramsey :<br />
<br />
Well, it was a great theory, but my test did not bear it out. Even<br />
>with 2D inputs the new index is still taking about 5x longer to return<br />
>a small result set as the old one. :(<br />
><br />
>P<br />
><br />
>On Thu, Dec 30, 2010 at 3:32 PM, Paul Ramsey
<pramsey@opengeo.org> wrote:<br />
>> You edit the postgis/gserialized.h file and define or undef GSERIALIZED_ON<br />
>><br />
>> BTW, I have a theory now which I just need to test... the data are 3D!<br />
>> And in fact the new GiST index will build an index WITH DIMENSIONALITY<br />
>> DETERMINED BY THE DATA. Not by the opclass. So the tree built with the<br />
>> new index is going to be more expensive to search in 2D than an actual<br />
>> 2D tree would have been. I just need to change my input data to 2D and<br />
>> see if the performances fall into line to confirm my guess.<br />
>><br />
>> P.<br />
>><br />
>> On Thu, Dec 30, 2010 at 12:50 AM, Andrea Peri
<aperi2007@gmail.com> wrote:<br />
>>><br />
>>>>On my lap top the loading and index building take about the same<br />
>>>>amount of time, but the query runs in about 1ms for the old index and<br />
>>>>about 5ms for the new one. My assumption (thus unconfirmed) is that<br />
>>><br />
>>>>the problem is not in the consistent checks (doing things like<br />
>>>>reducing the size of the slice detoasted to the minimum necessary for<br />
>>>>2d queries only improved the times by about 10%) but rather in the<br />
>>><br />
>>>>tree itself: that the new index is just building a crappier tree, so<br />
>>>>the query has to traverse more of it to get the same answer.<br />
>>><br />
>>> There even an increase of memory resource needed ?<br />
>>><br />
>>> To test this version there is a new key setting to apply in the .configure,<br />
>>><br />
>>> or need to change manually the definitions ?<br />
>>><br />
>>> --<br />
>>> -----------------<br />
>>> Andrea Peri<br />
>>> . . . . . . . . .<br />
>>> qwerty אטלעש<br />
>>> -----------------<br />
>>><br />
>>><br />
>>> _______________________________________________<br />
>>> postgis-devel mailing list<br />
>>> postgis-devel@postgis.refractions.net<br />
>>> http://postgis.refractions.net/mailman/listinfo/postgis-devel<br />
>>><br />
>>><br />
>><br />
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</aperi2007@gmail.com></pramsey@opengeo.org>
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