[mapguide-users] RE: Is their a major flaw with theming point data?

[Jason Birch]

How would you handle this James?

The spatial intersection that MapGuide performs with the current viewport's
extents is critical to performance when you are dealing with large amounts
of data, and many of the FDO data sources are optimized using R-Tree (or
similar) indices to return only the data which is currently in view.

I guess you could conceivably fetch an over-post of the current extents by
some factor, but that would only work for a subset of point symbols (those
where the maximum dimensions of the theming is < half the expanded extent
dimension, and it would mean that everyone has to live with the decreased
performance of the over-fetch.

A few options:
 - Make the over-fetch percentage or distance configurable per server, per
map, or per-layer
 - Only apply the over-fetch to points (there are actually cases where the
same problem happens with lines and polygons, so I don't think this is
valid)

I personally feel that the current behaviour is generally OK, but there are
definitely cases where you wouldn't want features missed just because their
mid-point isn't in the current view extents.

Regardless of the solution, I think this would take some work, so might
require some funding or somehow making it important to one of the
developers.

Jason


On 16 February 2010 12:06, JamesDudden  wrote:

> I understand how it happens and it does make sense but it renders the
> theming of points useless if they are going to be anything larger than a
> few
> pixels.
>
> I think it would be good to see future versions of Mapguide become more
> intelligent and be able to cope with theming of points.
>
>
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