Map file with 35,000+ Lines... management issue

Bob Basques Bob.Basques at CI.STPAUL.MN.US
Wed Jan 23 14:34:57 EST 2008


Ritz,

Whew, 35k lines, that big.  How many layers is that anyway?   The Googlish mapfile I just did only has 1100 lines in it, and that's mostly for readability.  I could probably get it down to half that size if I tried.

Don't know what I can contribute as a "Best Practice", because I feel that in most cases, that form follows function, if you need a capability, you build it.  Anyway, here are some of my thoughts.

These same sorts of performance questions crossed my mind too.  The Googlish mapfile I've been working on has 72 separate STYLE definitions for example.  Mostly ranged around threshholding of certain styles.  I can see that adding in the Water bodies, Railroad, Parks, and such, is really going to make this thing big.  I may just do those as separate MapFiles though since GeoMoose handles things like these separations very nicely.

These are some of the primary reasons that contributed to the way we've built GeoMoose as a client and why it runs against MapServer CGI, so that it can abstract the layer calls in this fashion.  We're running 135+ layers internally at the moment, and they all have their own MAPFILE and are all called separately from the client.  It has made life much easier with regard to MapFile creation and maintenance, since each data custodian handles their respective MAPFILE.  The performance issues are minimized well since even the data intensive layers are not too bad from a performance standpoint.

But even my Googlish looking mapfile got prettty big (in my opinion) for simply displaying centerlines of streets.   I've learned quite a bit from these exercises about these types of questions.  While I have yet to attack the performance side of things, I anticpate that I'll need to segregate the data out at differing thresholds in order to gain some performance boots.  We're all about doing dynamic requests here since many of our datasets change very frequently, in some cases, down to the minute.  I may look into tiling at some point in the future, but it will still be only for some of the layers, there will still be a need to have this dynamic request structure in place.

bobb



Bob Basques
GIS Systems Developer
City of Saint Paul, MN

GISmo 
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>>> riteshambastha <ritesh.linux at GMAIL.COM> wrote:

Dear Readers, 

I have developed a map file with more than 35,000 Lines. Its size will grow
by double/triple in next few months. Now, I am trying to tune my map file by
removing unwanted lines. Still, I am bit confused about its maintenance. 

Please throw some lights over writing map files by following best practices. 

Thanks in advance. 

Regards,
Ritz
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