Re: Witango-Talk: Distance Calculations - Sort on..., search on...

[Alan Wolfe]

I guess without more information here's the best solution that i see...   depending on number of users you have and number of locations they are looking at, it might be best to store the distances to each location the user cares about in the database (calc'ing them at some point) and then just sort that way.  calculating distance for alot of locations at one time is going to be alot of CPU and will take a long time no matter how you calc them (i am a game programmer on the side and deal w/ these kinds of problems all the time, if at all possible, pre-calculating distance and storing it is the way to go in alot of situations).  If the user is in a position to where they would be able to "relocate" themselves, if feasible, you could just recalculate the distances at the time they locate.   I think by far the best solution would be to store the data in the database if possible.   If not possible, if you have few enough locations, you could calculate distances on the fly, but if possible, having the database calculate the distance instead of witango since most databases seem to be better at doing massive amounts of math at a time then witango is.   another thing you could do is if your database supported views you could create a view where one of the columns on the view is the distance of the location, and then you could select data from the view and do sorts etc.   with more information, we could probably give better help but dont know if you would be giving away "proprietary secrets" or not to do so :P ----- Original Message ----- From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, October 31, 2004 11:18 AM Subject: Re: Witango-Talk: Distance Calculations - Sort on..., search on... Alan,   stored is only the altitude and longitude. So, no more informations. The rest is calculated.   rs   daniel     ----- Original Message ----- From: Alan Wolfe To: [EMAIL PROTECTED] Sent: Sunday, October 31, 2004 7:40 PM Subject: Re: Witango-Talk: Distance Calculations - Sort on..., search on... Hi Richard,   How is the list of locations generated and what do they represent?  how are you using them in your program?   Just wondering, why is it you want to store the formula-text in the database?  If the database gave you the answer instead of the formula, would you still need the text of the formula? ----- Original Message ----- From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, October 31, 2004 10:22 AM Subject: Witango-Talk: Distance Calculations - Sort on..., search on... Distance Calculation is no problem, that works. Here the formula: <@CALC EXPR="ACOS(SIN(@@User$Breite_1)*SIN(<@COLUMN 'Adressen.Geo_Breite'>) + COS(@@User$Breite_1)*COS(<@COLUMN 'Adressen.Geo_Breite'>)*COS(<@COLUMN 'Adressen.Geo_laenge'>-@@User$Laenge_1)) * 6378,388" Precision="1">   The problem what I have is:   1) To do a sort of the result (OK, I can do it in a array, but this need to much RAM [more as 2500 records, nearly 50x on one time])   2) To do a search in a specified area like "show me all points near x miles(km).   One way what make sense is to store the formula in the database, but - if i make a assign to a variable, then Witango store only the result. What I like to store is the formula-text:     Second problem: I can't do a sort on the stored formula (Sort command: <@COLUMN 'Adressen.formel' Encoding="Metahtml">)   Any Successions ?   THX for help   regards Daniel   ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf