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<p class=MsoNormal><span style='color:#1F497D'>GetGeometry (the one returning
an FdoByte *) has documentation that says the following:<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'>“The array's memory area is only
guaranteed to be valid until a call to ReadNext() or Close(), or the disposal
of this reader object.”<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'>So, the code is behaving
according to the specification. There should be a similar statement for
GetString, as well as any other accessor that returns a pointer to
non-reference-counted arrays, but I do not see one. Anyway, an FDO client
should expect the above behaviour from any FDO provider, even if it actually
does some internal copying.<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'>Regardless, it looks like the
behaviour that Haris sees is a defect. Different readers should not be sharing
an internal cursor.<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'>Gavin<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 lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Badreddine
Karoui<br>
<b>Sent:</b> Wednesday, August 13, 2008 4:14 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] RE: SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The free threaded
provider would use FdoThreadCapability_MultiThreaded defined in <a
href="https://svn.osgeo.org/fdo/trunk/Fdo/Unmanaged/Inc/Fdo/Connections/Capabilities/ThreadCapability.h">https://svn.osgeo.org/fdo/trunk/Fdo/Unmanaged/Inc/Fdo/Connections/Capabilities/ThreadCapability.h</a><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The SDF provider is
returning FdoThreadCapability_PerConnectionThreaded. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>I had a quick look
and I can see that the SDFSimpleFeatureReader::GetGeometry(FdoString*,
FdoInt32*) is returing the pointer from the internal buffer. This may have been
done to avoid paying the penalty of copying the geometry. The second oveload,
GetGeometry(FdoString*) is returing a copy and should not have the same issue. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>We may have to be
extra carefull in case we decide to fix this issue to make sure the reader
performance is not impacted. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Badreddine<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Haris
Kurtagic<br>
<b>Sent:</b> Wednesday, August 13, 2008 3:12 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] RE: SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>it looks that feature
readers are sharing same sqlite cursor with one data buffer. (BTW:
Application is sending this readers to be used by another app so it is not able
to create new buffers)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Hm, you have lost me
in this threading namings :)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Same SDF connection
can’t be shared across threads, right ? ( I thought that as thread safe )<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>I would like to
understand reasons for that behavior and if there are rooms for improvements.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Sqlite connection can
be shared between threads.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Thank you,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Haris<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Badreddine
Karoui<br>
<b>Sent:</b> Wednesday, August 13, 2008 8:36 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] RE: SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>It was not obvious
that the readers were on the same thread. In that case it’s a defect. Make sure
to copy the geometry before ReadNext is called. It’s possible the second
reader(ReadNext) is invalidating the geometry.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The SDF provider is
thread safe but not free threaded, it’s per-connection threaded.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Badreddine<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Haris
Kurtagic<br>
<b>Sent:</b> Wednesday, August 13, 2008 2:39 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] RE: SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>I was saying
for two feature readers inside same thread will result in error.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Also, i would like to
understand why SDF provider is not thread safe.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Haris<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'> <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Badreddine
Karoui<br>
<b>Sent:</b> Wednesday, August 13, 2008 8:18 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> [fdo-internals] RE: SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The SDF provider is
per connection threaded which means only one thread can access a reader at a
time. You can have many threads using their own connections/readers at the same
time.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Badreddine<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Haris
Kurtagic<br>
<b>Sent:</b> Wednesday, August 13, 2008 2:29 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> [fdo-internals] SDF feature reader <o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Hi,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I have issue when when more than one
feature reader is created against same SDF connection<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>It looks like same buffer ( created by
sqlite cursor ) is shared betwean feature readers.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>This will cause that data returned from
feature reader with function GetGeometry will be corrupted when another reader
is used.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Is this a bug or I am not looking into it
correctly ?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I would like to be able to use multi thread
access to sqlite database.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>If I am right, SDF provider is not “thread
safe” ? if so, what are main reasons for it ?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Thank you,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Haris<o:p></o:p></span></p>
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