[Mapserver-dev] Modification to iteminfo piece of variousconnections...

Steve Lime steve.lime at dnr.state.mn.us
Thu Mar 13 11:19:32 EST 2003


Hi Paul: Joins are being approached in the same way as layers. A wrapper
type interface with vendor specific code underneath. In fact, joins will
be applied within the maplayer.c code. In that sense they are very
generic since any specific driver could easily be added. I'm just
starting with MySQL since it's a pretty simple one, is OpenSource itself
and I personally can make use of it. The join structures themselves
mirror those of a layer with regards to connections so pooling amongst
joins and layers is certainly possible although I'll get things working
without it initially.

Steve

>>> Paul Ramsey <pramsey at refractions.net> 03/12/03 17:36 PM >>>
Joins are something we're quite interested right now, as we have a 
potential client with that particular need.  However, we're generally 
being asked to join to Oracle.  (a) how are you planning on structuring 
the MySQL data sources? How is data pulled into mapserver for 
processing for the join? (b) if we do MySQL, why not do generic 
database connectivity, using Jan's new connectionpool as the source for 
the db connections?

Paul

On Wednesday, March 12, 2003, at 02:08 PM, Steve Lime wrote:

> Hi Folks: In order to get dynamic joins working for query and
> classification I need to request that developers make a modification
to
> the routines that muck with the void *iteminfo layer variable.
> Previously it was assumed that the contents of the layer->items 
> variable
> were items related only to the core data (i.e. a single shapefile or 
> SDE
> query). With joins that's not the case. The items could come from the
> core data OR from a dynamic join. (I'm planning on DBF and MySQL 
> support
> for the 3.7 release) So, the vendor specific code needs to be altered 
> to
> take this into account. For example, for shapefiles iteminfo really is
> just a list of DBF item indexes for the items we need. I will change
> that so iteminfo is a pointer to a struct that contains an array of
> indexes plus the length of that array since we can't assume it's the
> same length as the layer->items array. I'll take care of the shapefile
> and SDE modifications, but will need help for the others. Clear as
mud?
> Contact me with questions...
>
> Steve
>
> Stephen Lime
> Data & Applications Manager
>
> Minnesota DNR
> 500 Lafayette Road
> St. Paul, MN 55155
> 651-297-2937
> _______________________________________________
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> Mapserver-dev at lists.gis.umn.edu
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