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<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>It’s a waste of space to
store BBOX. It would cost at least 32 bytes per feature, not counting the
indexes.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Also, you can easily compute the
bounding box and add those 4 columns very quickly when you need them, given
that SQLite is pretty fast to read from. Indexing on the 4 BBOX columns would
make spatial queries have to compute the intersection of the results of 4 tree
searches. SQLite is fast, but it’s not *<b>that</b>* fast.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Anyway, the nice thing about
this format is that you can create the BBOX columns anyway, and use them. The
FDO provider will not be using it though, for performance reasons.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Traian<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Kenneth,
GEOGRAF A/S<br>
<b>Sent:</b> Tuesday, March 25, 2008 7:12 AM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> Re: [fdo-internals] FDO RFC 16 - FDO Provider for SQLite<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I just re-read the RFC.<br>
<br>
What are your reasons for not storing BBOX releated data in the data table?<span
style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><br>
<br>
I would suggest adding four columns, like minx, maxx, miny, max (perhaps name
them via. the geometry_columns table?).<br>
With that approach, and index on the pairs would move the BBOX query
load/optimization into the DBMS.<br>
BBOX queries are simple, and does not require reading the actual column data.<br>
<br>
Your extended spatial index algorithm might read these values to produce the
search tree.<br>
<br>
Another suggestion, would be to store the search tree in a blob column.<br>
That would enable a much faster load of data.<br>
<br>
To avoid the requirement that all data updaters know the algorithm, it might be
legal to just clear the BLOB data on updates.<br>
<br>
I wrote a short paper on a similar mechanism some time ago, with a friend:<br>
<a href="http://www.hexad.dk/opensource/spatialdbms.pdf">http://www.hexad.dk/opensource/spatialdbms.pdf</a><br>
<br>
<br>
<br>
<o:p></o:p></p>
<pre>Regards, Kenneth, GEOGRAF A/S<o:p></o:p></pre>
<p class=MsoNormal><br>
<br>
Traian Stanev skrev: <o:p></o:p></p>
<p class=MsoNormal>Hello,<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>I just posted FDO RFC #16. Fresh off the virtual presses
(printed on 100% recycled electrons, for you green-minded folks):<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal><a href="http://trac.osgeo.org/fdo/wiki/FDORfc16">http://trac.osgeo.org/fdo/wiki/FDORfc16</a><o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Thanks,<o:p></o:p></p>
<p class=MsoNormal>Traian<o:p></o:p></p>
<pre><o:p> </o:p></pre><pre style='text-align:center'>
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href="mailto:fdo-internals@lists.osgeo.org">fdo-internals@lists.osgeo.org</a><o:p></o:p></pre><pre><a
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