OGR ODBC spatial query has invalid resultset

[Delfos, Jacob]

Hi Frank,

Thanks a lot for that. It works great. That's really saved my neck.

Regards,

Jacob
 

> -----Original Message-----
> From: Frank Warmerdam [mailto:warmerdam at pobox.com] 
> Sent: 26 September 2006 21:08
> To: Delfos, Jacob
> Cc: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-USERS] OGR ODBC spatial query has 
> invalid resultset
> 
> Delfos, Jacob wrote:
> > Hi List,
> > 
> > Sorry about all the questions I have been sending. I'm 
> hoping someone 
> > can shed light on this one.
> > 
> > After a QueryByPoint or QueryByRect operation in PHP, the number of 
> > results is correct, but the resultCacheMemberObj always 
> points to the 
> > first "getNumResults()" objects. If there are 4 results, it holds 
> > references to objects 1-4. For one result, it always points 
> to the 1st 
> > object.
> > 
> > This is -not- the case for QueryByAttributes, though. The 
> > resultCacheMemberObj is correct for this type of query.
> > 
> > This only occurs for OGR ODBC layers. I have tried MDB and 
> CSV, with the 
> > same problem...
> > 
> > If anyone knows why, please let me know. If someone thinks 
> this is a 
> > bug, I'll file it.
> 
> Jacob,
> 
> This occurs with OGR ODBC datasources that lack an FID column 
> in the original
> table.  Without an FID, OGR just assigns FIDs starting with 
> zero to the
> result set.
> 
> The problem really bites when different constraints (spatial 
> or attribute)
> are in place at the point where the query is done, and when 
> the results are
> fetched - which is the case when you do spatial queries as 
> the spatial query
> apparently is cleared by mapserver before it starts fetching 
> individual
> results.
> 
> The overall point is that two-stage queries (as done by mapserver) are
> very unreliable against OGR datasources without a persistent 
> FID, such as
> some ODBC datasources.
> 
> BTW, you can use the mapserver config variable ODBC_OGR_FID 
> to force the
> ODBC driver to pick a particular column as the FID.  
> Unfortunately this
> is a global option so it only works smoothly if you have the same name
> for the id of all tables you are accessing in a given 
> mapserver map.  You
> would add something like the following in the MAP section of 
> your map file
> to default to using the ID column of your odbc tables as the 
> feature id.
> 
>    CONFIG "ODBC_OGR_FID" "ID"
> 
> Best regards,
> -- 
> ---------------------------------------+----------------------
> ----------------
> I set the clouds in motion - turn up   | Frank Warmerdam, 
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, 
> http://osgeo.org
> 
>