[gdal-dev] how to use the filter option -where within an mysql request?

[Stefan Schantz]

Hi again,
I 've tried it now with
ogrinfo --version
GDAL 1.8.0, released 2011/01/12

but with the same negative result:

without any filter, I get results like

OGRFeature(sql_statement):1677
   value (Real) =             99.215000
   end_measure (DateTime) = 2011/12/20  0:00:00
   POINT (8.64381981 50.6018486)

with the filter option "-where"
ogrinfo -ro 
MYSQL:onmon,host=10.130.63.11,user=user,password=pasword,port=3306,tables=result_current 
-SQL "SELECT value, end_measure,locality.geom from result_current JOIN 
locality on result_current.locality_code =locality.locality_code" -where 
"end_measure = '2011/12/20 0:00:00'"

I didn't get any hits.

Any idea?

Best regards,
Stefan


Am 20.12.2011 13:50, schrieb Even Rouault:
> Stefan,
>
> Please always mention the GDAL/OGR version you are using in your reports. It
> will save the readers from figuring out from the error message that you must use
> GDAL 1.7.x or an earlier version.
>
> The -where "end_measure = '2011-12-20'" clause doesn't work in GDAL 1.7.x or
> earlier because the code didn't support comparison on DateTime fields (the error
> message mentions list of binary fields, but DateTime fields too)
>
> I've done a quick test on GDAL 1.9.0beta1 and you can use comparisons on date,
> but they seem to be string based. And you have to respect the format of the
> string serialization used by OGR. In your case, it would be -where "end_measure
> = '2011/12/20  0:00:00'"
>
> However, there's no advantage of using -where when you already use -sql. The
> -sql is directly forwarded to the SQL engine of the RDBMS (when the OGR driver
> is the one of a RDBMS of course), so it will run faster than -where which,
> depending on situations, can be evaluated on OGR side.
> - On a layer which is already the result of -sql, the -where clause is always
> evaluated on OGR side, after the evaluation of -sql
> - If the layer is directly a table name, then the -where clause is generally
> forwarded to the server. (It might depend on the OGR driver however).
>
> So, as a rule of thumb, you can remember that there's no point in using both
> -sql and -where.
>
> Best regards,
>
> Even
>