[postgis-devel] Calling Index Genii

[Paul Ramsey]

Well, it was a great theory, but my test did not bear it out. Even
with 2D inputs the new index is still taking about 5x longer to return
a small result set as the old one. :(

P

On Thu, Dec 30, 2010 at 3:32 PM, Paul Ramsey <pramsey at opengeo.org> wrote:
> You edit the postgis/gserialized.h file and define or undef GSERIALIZED_ON
>
> BTW, I have a theory now which I just need to test... the data are 3D!
> And in fact the new GiST index will build an index WITH DIMENSIONALITY
> DETERMINED BY THE DATA. Not by the opclass. So the tree built with the
> new index is going to be more expensive to search in 2D than an actual
> 2D tree would have been. I just need to change my input data to 2D and
> see if the performances fall into line to confirm my guess.
>
> P.
>
> On Thu, Dec 30, 2010 at 12:50 AM, Andrea Peri <aperi2007 at gmail.com> wrote:
>>
>>>On my lap top the loading and index building take about the same
>>>amount of time, but the query runs in about 1ms for the old index and
>>>about 5ms for the new one. My assumption (thus unconfirmed) is that
>>
>>>the problem is not in the consistent checks (doing things like
>>>reducing the size of the slice detoasted to the minimum necessary for
>>>2d queries only improved the times by about 10%) but rather in the
>>
>>>tree itself: that the new index is just building a crappier tree, so
>>>the query has to traverse more of it to get the same answer.
>>
>> There even an increase of memory resource needed ?
>>
>> To test this version there is a new key setting to apply in the .configure,
>>
>> or need to change manually the definitions ?
>>
>> --
>> -----------------
>> Andrea Peri
>> . . . . . . . . .
>> qwerty àèìòù
>> -----------------
>>
>>
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>