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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>Many relational databases allow fields to be set to NULL. Is
this supported in OGR? How does one detect whether a field is nullable or not?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>Looking at the class documentation, I see functions
OGRFeature::IsFieldSet and OGRFeature::UnsetField. Are these intended for checking
whether a field is NULL and setting it to NULL? Or are they used for something else,
such as determining which fields have been modified by a caller prior to him
calling OGRLayer::SetFeature?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>When I looked at OGRFieldDefn, I could not find a method that
might be intended for checking whether a field was nullable (e.g.
OGRFieldDefn::IsUnsettable).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>A while back, Mateusz asked this:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>><i>
Yes. Also, most applications I've seen using OGR do define their own<o:p></o:p></i></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>><i>
data models and translate OGRFeature to features of their own types.<o:p></o:p></i></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>><i>
Perhaps it would be interesting to know why they don't use OGRFeature<o:p></o:p></i></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>><i>
as a part of their data model, what's missing...<o:p></o:p></i></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>I am currently evaluating whether or not I should use OGRFeature
directly in a data model, or wrap it. Without nullability, I am probably
inclined to wrap it. As I have mentioned previously on gdal-dev, I'm trying to
build something that wraps OGR and ArcGIS APIs behind a common abstraction, to
allow development of tools that work with both. ArcGIS supports nullability and
it is useful in many situations, so I'd like to cleanly preserve it in my
abstraction, even if OGR does not presently support it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>Thanks for any thoughts you have,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'>Jason<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#003399'><o:p> </o:p></span></p>
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