[mapserver-users] MapInfo "Seamless" layer performance issues

[Martin, Daniel]

I'm trying to use MapInfo Seamless layers in MapServer.  They do work, which
is great.  But they are slow relative to the individual layers.  To
elaborate, I have one Postal Code layer per state.  To treat them as a
single layer for a National mapping application, I have created a "Seamless"
layer to pull them all together.

Now, I expect that to be slow.  Even pulling it into MapInfo is slow.  It's
a huge amount of data.  However, if I zoom in to a scale of a few miles, I
should only be loading one layer because I can only see one state.  But even
this is very slow.  If I load the same map using the actual physical layer
rather than the seamless, it's pretty fast, even though it's displaying the
same data.  Even if I merge the entire national Postal Code dataset into one
gigantic layer, it performs fairly fast, so the issue cannot be in the
volume of data.  Specifically this last example doesn't seem to make sense.
And the performance difference is minutes as opposed to seconds, Seamless
vs. normal.

Is there something I can do to improve performance of a Seamless layer?  Or
is it just a reality, and I should look to combining my data.

Thanks, 
Dan Martin