[Mapserver-users] Filtering a shape file using a list ofrecord keys

[James Perrins]

Steve,

Many thanks for this - I'm new to mapserver and have been searching the
archive for details on this.  I think I now more or less understand what
can and can't be done in this area (a moments excitement when I found
the current JOIN function - but then I discovered what it was really
for).  I've found a variety of ways to filter and to dynamically plot
points, but they all look as if they will only work for a few records
(or maybe a few 100) due to string length issues.

Dynamic JOIN in 3.7 sounds just what I'm after - any idea when this
might be up and running ?- in the mean time I've been looking at writing
out temporary shape files as I'm only bothered about points for the
moment.

Best wishes
James

-----Original Message-----
From: Steve Lime [mailto:steve.lime at dnr.state.mn.us] 
Sent: 19 March 2003 19:37
To: JamesP at esdm.co.uk; JamesPerrins at esdm.co.uk;
mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] Filtering a shape file using a list
ofrecord keys

There's no built-in limit to expression length, but I bet bison has one
built in. Don't know if you're using it or not but there is an "IN"
operator that allows you to compare one value to a list of values.

As for workarounds, depends on how you're building the list of keys.
Cached queries might be one way. When true dynamic join support hits
with 3.7 that may work as well, but it's not working yet...

Steve

>>> JamesP at esdm.co.uk 03/13/03 06:33PM >>>
Hi,

 

What is the best way to filter a shape file using a list of record
keys.

 

Presumably I can build up a string in CLASS EXPRESSION - but if I am
selecting a lot of objects, this could get quite a lengthy string - is
there a limit to the number of characters that this will take ?

 

Is there a better way of doing this - e.g. joining in a dbf file
containing the list of keys ?

 

Many thanks in advance

 

James Perrins