[gdal-dev] OGR_L_SetAttributeFilter

[Even Rouault]

Hi Paul,

The reference for OGR SQL is http://gdal.org/ogr_sql.html (I'm not sure how 
relevant this ogdi page is)

"fid" is indeed a special field in OGR SQL. I'm not sure if it is really 
specified how that is supposed to work when a layer has a regular field also 
called "fid". From a quick testing, it seems that the regular field "fid" will be 
selected.

Regarding quoting of columns or tables, this is the regular SQL rule.  For 
safety, you might systematically want to double quote them.

Even

On Friday 29 April 2016 19:42:20 Paul Ramsey wrote:
> A new question not answered: what is the current specification for SQL
> filters in SetAttributeFilter? Has it evolved beyond this spec
> (referenced from the GDAL docs)
> http://ogdi.sourceforge.net/prop/6.2.CapabilitiesMetadata.html
> 
> P.
> 
> On Fri, Apr 29, 2016 at 12:19 PM, Paul Ramsey <pramsey at cleverelephant.ca> 
wrote:
> > In answer to myself, quoting the offending columns (eg "2name") allows
> > otherwise illegal column names to find their way to GDAL's filtering
> > machinery.
> > 
> > Another question, which I seem to have an answer for: is "fid" a magic
> > column name that will address the OGR fid? It seems to be, which is
> > pretty amazing. What happens if an OGR table also has a legit field
> > named "fid"?
> > 
> > P
> > 
> > On Thu, Apr 28, 2016 at 7:21 PM, Paul Ramsey <pramsey at cleverelephant.ca> 
wrote:
> >> http://www.gdal.org/ogr__api_8h.html#a4000d426bf26ad7cc7d4012634c93f09
> >> 
> >> So, the reference to valid attribute filters points to
> >> 
> >> http://ogdi.sourceforge.net/prop/6.2.CapabilitiesMetadata.html
> >> 
> >> And there it says that
> >> 
> >> @field_name@ = @string_token@
> >> 
> >> and that
> >> 
> >> "The @string_token@ starts with a character in a-z,A-Z and is followed
> >> by any number of characters in the set a-z,A-Z,0-9 and underscore."
> >> 
> >> Now, OGR layer names can be quite a bit more complicated than that,
> >> coming as they do from crazy data sources like FGDB, or even shape
> >> file! So 'b-rthday' is a perfectly legal shape file attribute name, as
> >> is 'Field Survey' from FGDB.
> >> 
> >> How do we address those column names?
> >> 
> >> I'm working in the FDW space, and have a mapping between PgSQL column
> >> names (simple, not unlike the rule from the referenced document) to
> >> OGR column names (crazy shit potentially). I figured I'd just re-write
> >> the SQL to use the OGR names, and then boom, things would work, but it
> >> turns out that OGR doesn't want to accept filters using the very
> >> column names OGR has inside... so... what should we feed it?
> >> 
> >> P
> 
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