[mapguide-dev] Enhanced Join Support RFC

[Ronnie Louie]

Hi Jason,

 

Thanks for your comments.  Your suggestions for handling 1:many are duly
noted, however it is not proposed as part of this RFC.  As Bob mentioned
earlier in a previous email, the join functionality is implemented via a
Join component which is also shared with another commercially available
product.  Changes were discussed to support "associations" of a primary
feature record to a set of secondary records, but ultimately did not
make it into that product's release cycle.  I can only speculate that
this support may be part of a future release.  As a result, MapGuide
will be restricted, for now, to the "lazy join" result for the 1:many
case.

 

As for your question on the SDF joins, it should be possible to join
secondary table to a primary table in the same SDF or different SDF
file.  I haven't personally tested this, but if you've got SDFs with
multiple tables, you should be able to see a list of all the available
feature classes in the Studio Join UI for which you can use to define
you join.

 

Ronnie

 

 

 

  _____  

From: Jason Birch [mailto:Jason.Birch at nanaimo.ca] 
Sent: Friday, November 03, 2006 4:21 PM
To: dev at mapguide.osgeo.org
Subject: RE: [mapguide-dev] Enhanced Join Support RFC

 

Overall, I like this proposal.  I think that the 1:many support is
probably a good first step.  It makes it easier to query secondary data
sources and return geometry.  

 

However, it is really just a right outer join, and does not provide for
some of the most common map operations that will be required with 1:Many
relationships.

 

In particular, it will not be able to support maptips (display all
owners for a parcel), queries (only show properties with more than one
service connection) and theming (color ramp based on number of calls for
service)

 

I think that this would be best dealt with in two ways.  First, I would
like to see an option to return a single geometry row, with a nested
rowset representing the "Many" records.  Second, I would like to see the
option to return a single geometry row along with some basic aggregate
(sum, min, max, mean, group_concat) and search (contains) results,
essentially acting as a GROUP BY operator on the root geometry.  These
could even be combined, allowing both the aggregate functions and the
nested results to be returned.  

 

I understand that this is a big request, but I thought I'd reiterate it
here.  It was discussed in IRC after the last meeting, but I don't have
the logs.

 

I also have a question about why spatial and aspatial data sources are
so segregated in Studio.  I may just be a bit fuzzy, but is it possible
to join a secondary table in an SDF file to a primary table in the same
SDF file?  In another SDF file?

 

Jason

 

  _____  

From: Ronnie Louie
Sent: Fri 2006-11-03 2:48 PM
To: dev at mapguide.osgeo.org
Subject: [mapguide-dev] Enhanced Join Support RFC

Hi All,

 

A first draft of Enhanced Join Support RFC for MGOS is posted at
http://wiki.osgeo.org/index.php/MapGuide_RFC_5_-_Enhanced_Join_Support.

 

Please have a look and post your feedback to this group.

 

Thanks

Ronnie Louie

 

 

 

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