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<TITLE>RE: [postgis-devel] Does ST_Max_Distance work on anyone's install</TITLE>
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<P><FONT SIZE=2>Ah okay I agree with Strk on that one.<BR>
<BR>
For the example he gave I would expect<BR>
it to return 10 too since I think the common use case would be for example<BR>
<BR>
Given a road a and road b -- what's the furthest that anyone would need to trek<BR>
(excluding routing obstacles) from anywhere on road a to get to anywhere on road b.<BR>
<BR>
Hmm I wonder how much effort it would be to fix it. I guess strk gave up on it<BR>
so that would mean I am probably too stupid to attempt it. Pity though.<BR>
<BR>
Well as functions go I guess its not the most important thing. Would be more useful for polygons anyway since city to city commuting is more interesting.<BR>
<BR>
-----Original Message-----<BR>
From: postgis-devel-bounces@postgis.refractions.net on behalf of Paul Ramsey<BR>
Sent: Wed 10/29/2008 12:23 PM<BR>
To: PostGIS Development Discussion<BR>
Subject: Re: [postgis-devel] Does ST_Max_Distance work on anyone's install<BR>
<BR>
And there's the answer:<BR>
<BR>
<A HREF="http://postgis.refractions.net/pipermail/postgis-devel/2004-August/000437.html">http://postgis.refractions.net/pipermail/postgis-devel/2004-August/000437.html</A><BR>
<BR>
On Wed, Oct 29, 2008 at 9:21 AM, Paul Ramsey <pramsey@cleverelephant.ca> wrote:<BR>
> I'm pretty sure it existed and worked at one point, because Dave wrote<BR>
> it originally for a particular data processing use case Refractions<BR>
> had. Why strk turned it off is for him to say :)<BR>
><BR>
> P.<BR>
><BR>
> On Wed, Oct 29, 2008 at 4:17 AM, Mark Cave-Ayland<BR>
> <mark.cave-ayland@siriusit.co.uk> wrote:<BR>
>> Obe, Regina wrote:<BR>
>>><BR>
>>> <A HREF="http://postgis.refractions.net/documentation/manual-svn/ST_Max_Distance">http://postgis.refractions.net/documentation/manual-svn/ST_Max_Distance</A>.<BR>
>>> html<BR>
>>><BR>
>>> I noticed Robert Burgholzer tried to use it and couldn't either<BR>
>>> evidentally. Though I thought it worked once upon a time.<BR>
>><BR>
>> Strange. There is actually code in the function to "do things"TM but the<BR>
>> elog() at the top of the function causes it to exit straightaway!<BR>
>><BR>
>> Looking at svn log you can see the following comments:<BR>
>><BR>
>> ------------------------------------------------------------------------<BR>
>> r756 | strk | 2004-08-26 17:55:09 +0100 (Thu, 26 Aug 2004) | 2 lines<BR>
>><BR>
>> max_distance() raises an 'unimplemented yet' error.<BR>
>><BR>
>> ------------------------------------------------------------------------<BR>
>><BR>
>> ...<BR>
>><BR>
>> ------------------------------------------------------------------------<BR>
>> r753 | strk | 2004-08-26 16:02:59 +0100 (Thu, 26 Aug 2004) | 2 lines<BR>
>><BR>
>> Added (bogus) max_distance(geom,geom)<BR>
>><BR>
>> ------------------------------------------------------------------------<BR>
>><BR>
>><BR>
>> And the relevant commit diff is:<BR>
>><BR>
>> pg83@zeno:~/src/postgis-svn/trunk/lwgeom$ svn diff -r 755:756<BR>
>> lwgeom_functions_basic.c<BR>
>> Index: lwgeom_functions_basic.c<BR>
>> ===================================================================<BR>
>> --- lwgeom_functions_basic.c (revision 755)<BR>
>> +++ lwgeom_functions_basic.c (revision 756)<BR>
>> @@ -1735,6 +1735,9 @@<BR>
>> double maxdist = 0;<BR>
>> int i;<BR>
>><BR>
>> + elog(ERROR, "This function is unimplemented yet");<BR>
>> + PG_RETURN_NULL();<BR>
>> +<BR>
>> geom1 = (LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));<BR>
>> line1 = lwline_deserialize(SERIALIZED_FORM(geom1));<BR>
>> if ( line1 == NULL ) PG_RETURN_NULL(); // not a linestring<BR>
>><BR>
>><BR>
>> I'd say from this that strk had a go at implementing this function but<BR>
>> realised it didn't work properly and so disabled it soon afterwards :(<BR>
>><BR>
>><BR>
>> HTH,<BR>
>><BR>
>> Mark.<BR>
>><BR>
>> --<BR>
>> Mark Cave-Ayland<BR>
>> Sirius Corporation - The Open Source Experts<BR>
>> <A HREF="http://www.siriusit.co.uk">http://www.siriusit.co.uk</A><BR>
>> T: +44 870 608 0063<BR>
>> _______________________________________________<BR>
>> postgis-devel mailing list<BR>
>> postgis-devel@postgis.refractions.net<BR>
>> <A HREF="http://postgis.refractions.net/mailman/listinfo/postgis-devel">http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR>
>><BR>
><BR>
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