shptree not faster than no index

[ANDY CANFIELD]

I'd go with the one file of all counties. It's just easier to maintain one
file than 3,000. I have at least 50 layers in one of my maps that each layer
can have 300,000 to 1,000,000 plus objects in it. Using the shptree to
create a .qix file makes these layers incredibly fast. I mean fast as in,
you click on the map to zoom or pan, and as fast as your browser can render
the map has been updated to reflect that pan or zoom. I think my smallest
layer has 1,400 hundred polygons in it. Using the shptree and having one
file is way easier than maintaining a single file for each boundary. I
honestly don't think the map I'm using could be any faster, it is the
browser/desktop rendering speed for me that limits how fast the image
changes, so that's really, really fast. Plus if you have 3,000 files and are
zoomed to an extent where you can see half of them or more that's 1,500 or
more open and read operations that Mapserver has to execute vice one if you
put them all in the same file. My two cents anyway.


>From: John Bolster <jb at NUCOMP.COM>
>Reply-To: John Bolster <jb at NUCOMP.COM>
>To: MAPSERVER-USERS at LISTS.UMN.EDU
>Subject: Re: [UMN_MAPSERVER-USERS] shptree not faster than no index
>Date: Thu, 23 Sep 2004 18:18:46 -0400
>
>Thank you for your quick response.
>
>In terms of the county outlines, do you think that one county per file, and
>selecting which files to use with only a tileindex would be faster than all
>counties being in one huge file of over 3000 counties and selecting which
>counties to draw using a qix index?
>
>Also, does the qix index on the actual tileindex do anything to speed up
>the
>tileindex?
>
>Thanks,
>John
>
> > -----Original Message-----
> > From: Frank Warmerdam [mailto:warmerdam at pobox.com]
> > Sent: Thursday, September 23, 2004 6:13 PM
> > To: John Bolster
> > Cc: MAPSERVER-USERS at LISTS.UMN.EDU
> > Subject: Re: [UMN_MAPSERVER-USERS] shptree not faster than no index
> >
> >
> > John Bolster wrote:
> > > Hi all,
> > >
> > > I'm noticing there doesn't seem to be any difference in speed
> > between having
> > > *.qix files vs. not having them. I'm wondering if I'm doing this
>right.
> > >
> > > My data is from tiger and is in shapefiles. I'm only dealing with
>county
> > > outlines right now. They are each in a separate folder, each state's
> > > counties are in one state folder. There's a tileindex on them all at
>the
> > > root of the tree.
> >
> > John,
> >
> > The impression I get is that you have exactly one county polygon
> > per shapefile.
> > Is that right?  A .qix won't help because it is used to more
> > quickly select
> > the subset of shapes in a shapefile based on the extents.  If you
> > only have
> > one shape per file then it can't help.
> >
> > Of course, the tileindex should allow you to quickly select the county
> > files you want.  But a more efficient approach would likely be to have
>one
> > shapefile with a .qix with all your county outlines in it.
> >
> > Best regards,
> > --
> > ---------------------------------------+--------------------------
> > ------------
> > I set the clouds in motion - turn up   | Frank Warmerdam,
> > warmerdam at pobox.com
> > light and sound - activate the windows | http://pobox.com/~warmerdam
> > and watch the world go round - Rush    | Geospatial Programmer for Rent
> >
> >

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