problem with expression: null values in table

[Umberto Nicoletti]

On 10/8/07, Bart van den Eijnden <bartvde at gmail.com> wrote:
> Hi Umberto,
>
> thanks for the explanation.
>
> So this means with shapefiles in 5.0 null values would fall into the
> category of ([mycolumn] = 0) ? That seems almost even worse to me than an
> error ....

I think I have done so to achieve consistent behaviour with the
postgis and oracle providers.

>
> Mapserver really needs the concept of null values, but I can imagine this
> would require quite a bit of work ...

It is a lot of work, indeed.

Umberto

>
> Best regards,
> Bart
>
>
> On 10/8/07, Umberto Nicoletti <umberto.nicoletti at gmail.com> wrote:
> > Probably when the column is null it is evaluated by OGR to the empty
> > string and the expression (after replacing [HINDERCATEGORIE] with '')
> > becomes ' = 1' which is invalid.
> >
> > Just a side note: starting with mapserver 5 the shapefile provider
> > will return 0 for null numeric columns and '' for null strings.
> >
> > Umberto
> >
> > On 10/8/07, Bart van den Eijnden < bartvde at gmail.com> wrote:
> > > Hi list,
> > >
> > > I am posting this problem here since I don't know if it is an OGR
> problem or
> > > a Mapserver problem.
> > >
> > > Using Mapserver 5.0 and GDAL 1.4.1 we have an Oracle table that only
> > > contains null values for an integer column called HINDERCATEGORIE.
> > >
> > > The expression used in Mapserver is:
> > >
> > > EXPRESSION ([HINDERCATEGORIE] = 1)
> > >
> > > which will result in:
> > >
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > >  msyyparse(): Expression parser error. parse error
> > >
> > > [bart at hades rwsnl]$ shp2img -m topografie.map -all_debug 10 -l
> > > vaarwegwerkzaamheid_live -o /tmp/bla.png
> > > msOGRFileOpen(vaarwegwerkzaamheid_live.ovf)...
> > >
> OGROPen(/data/OGC_UMN_services/rwsnl/./vaarwegwerkzaamheid_live.ovf)
> > > msyyparse(): Expression parser error. parse error
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > > msyyparse(): Expression parser error. parse error
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > > msyyparse(): Expression parser error. parse error
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > > msyyparse(): Expression parser error. parse error
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > > msyyparse(): Expression parser error. parse error
> > > msEvalExpression: Expression parser error. Failed to parse expression:
> = 1
> > > msOGRLayerClose(vaarwegwerkzaamheid_live.ovf).
> > >
> msOGRFileClose(/data/OGC_UMN_services/rwsnl/./vaarwegwerkzaamheid_live.ovf,0).
> > > msDrawMap(): Layer 3 (vaarwegwerkzaamheid_live), 0.761s
> > > msDrawLabelCacheGD(): labelcache_map_edge_buffer = -10
> > > msDrawMap(): Drawing Label Cache, 0.005s
> > > msDrawMap() total time: 0.781s
> > >
> > > The layer definition is:
> > >
> > >   LAYER
> > >     NAME "vaarwegwerkzaamheid_live"
> > >     TYPE POINT
> > >     CONNECTIONTYPE OGR
> > >     CONNECTION "vaarwegwerkzaamheid_live.ovf"
> > >     DATA "vaarwegwerkzaamheid"
> > >     PROCESSING "CLOSE_CONNECTION=DEFER"
> > >     PROJECTION
> > >       "init=epsg:28992"
> > >     END
> > >     METADATA
> > >       "WMS_TITLE" "Vaarwegwerkzaamheden - staging omgeving"
> > >     END
> > >     CLASS
> > >       NAME "Unknown"
> > >       EXPRESSION ([HINDERCATEGORIE] = 1)
> > >       STYLE
> > >         ANGLE 360
> > >         COLOR 0 0 0
> > >         OPACITY 100
> > >         SYMBOL "wegwerkzaamheid_3"
> > >       END
> > >     END
> > >   END
> > >
> > > Best regards,
> > > Bart
> > >
> > >
> >
>
>