[gdal-dev] Padding/spacing in mysql driver output

[Even Rouault]

Hi,

this behaviour is not specific to the MySQL driver. When a field has a 
specified width and precision, it will get formatted according to it. This 
behaviour was specifically introduced 10 years ago ! : 
http://trac.osgeo.org/gdal/changeset/745. So it looks like a behaviour by 
design, although I'm not clear on its justification. Maybe Frank will 
remember ?

If you look at the first lines of your ogrinfo dump, you'll see that the 
fields with left padding are declared in the form :
lat: Real(22.0)

One possible workaround is that you change your MySQL table definitions so 
that the columns are not of the form double(x,y) but just double.

Another one, quite inelegant and possibly not performing well, is to embed the 
content of your ovf file into another ovf file and use the CAST operator of 
OGR SQL (see http://gdal.org/ogr/ogr_sql.html)

For example:

<OGRVRTDataSource>
    <OGRVRTLayer name="poly">
        <SrcDataSource> <!-- here put your original OVF file, but 
XML-escaped -->
            &lt;OGRVRTDataSource&gt;
                &lt;OGRVRTLayer name="poly"&gt;
                    &lt;SrcDataSource&gt;MYSQL:even&lt;/SrcDataSource&gt;
                    &lt;SrcSQL&gt;SELECT area FROM poly&lt;/SrcSQL&gt;
                &lt;/OGRVRTLayer&gt;
            &lt;/OGRVRTDataSource&gt;
        </SrcDataSource>
	<!-- here cast every double field as float(1) -->
        <SrcSQL>SELECT CAST(area as float(1)) FROM poly</SrcSQL>
    </OGRVRTLayer>
</OGRVRTDataSource>

Best regards,
Even

Le Sunday 19 April 2009 09:32:31 P.Romero, vous avez écrit :
> Hi,
> Im new to this list.
> I use ogr w/ the mysql driver as part of a mapserver installation.
>
> Im having an issue with the formatting of numeric results that are being
> returned from a mysql query.
> It appears that values originating from 'double'-typed fields in the MySQL
> database are showing up in ogr's output with a large amount of 'blank
> space' left-padding.
>
> Here's an example of some output from running "ogrinfo -al
> 'myQueryFile.ovf'":
>
> OGRFeature(mypoints):86
>   max(recTS) (Integer) = 1240078380
>   buoyName (String) = 51202
>   lat (Real) =                     21
>   lon (Real) =                   -158
>   MAG (Real) =                    -371
>   WDIR (Real) =                    -99
>   WSPD (Real) =                    -99
>   ADIR (Real) =                      81
>   ts (DateTime) = 2009/04/04  0:43:00
>   POINT (-157.680000000000007 21.420000000000002 0)
>
> In case my hotmail account mangles the above output, here is a description
> of what is occuring:
> Any value with a datatype of 'Real' (i.e., 'double' in MySQL) is appearing
> with approx. 20 spaces of left-padding. However, other datatypes are not
> showing this large padding.
>
> The extra spacing is also showing up in my mapserver ogr/mysql query
> output; its unnecessary, unwanted, & unacceptable, so Id like to remove it.
>
> Is this spacing a bug, or by design?
> How can I go about removing it from ogr's query results?
>
> Thanks in advance,
> P.Romero
>
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