Need support to specify geom column and select list with OGR, ODBC

[Frank Warmerdam]

On 10/12/05, Tamas Szekeres <szekeres.tamas at freemail.hu> wrote:
> Hi list,
>
> It would be greatly usable to support for specifying the geometry column
> when using OGR ODBC driver.
> The current implementation retrieves the geometry_columns table from the
> database in order to determine the geometry column of the table which
> causes an extra round trip to the server. For a suitable solution the
> geometry column name could be specified in the connection string as the
> table name.

Tamas,

First, this question belongs on gdal-dev more than mapserver-users.

Doing this would require some code changes but could be done.
My concern though is that I hate making the connection string
handling too complicated.

Is the query of the geometry_columns table really a significant
performance issue?

> It would be also helpful to establish the ability to specify the list of
> the columns to select, what could restrict the amount of the data as the
> user's will.

I am contemplating at some point extending the OGR API to allow
indicating what record elements are desired (geometry? which fields?)
as an optimization for performance.  However, it isn't too likely to happen
immediately.

Note that you can accomplish similar effects by using a custom
SQL SELECT statement in the DATA field in MapServer instead
of using a predefined table name.   There are downsides to this
approach if you are using the query mechanism of mapserver though.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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