New distance-calculations proposal

[nicklas]

A hopefully more structured ticket than #137

The patch attached includes:
new functions:

1. st_shortestline
   
2. st_longestline
   
3. st_dfullywithin
   
4. st_max_distance
   (this is really a fix to a long standing bug — st_max_distance has existed since at least 1.2 but has never worked - (older versions give Not yet implemented))

enhancements affecting st_distance, st_dwithin and the functions above:

1. a better handling of "holes" in polygons.
   
2. a sudden stop in iteration when the distance in st_dwithin is satisfied. Before it was checked for every subgeom.
   
3. a new way of calculating distances between lines and polygons that don't intersect.
   

Probably the last one is the most important. On big geometries it makes a big difference.

Beside the patch I have attached a document where I try to explain the idea behind the distance-calculation.

/Nicklas

[nicklas]

explanation of the distance calculation

[robe]

Nick,

Does this particular patch include the fix for ST_Max_Distance as well (i saw it in the patch you sent). I know you had it in a separate patch and I said to hold it separately since it was a fix to a long standing bug and not an enhancement. Though not sure how everyone feels about back-porting that particular fix to 1.4.1 since 1.4 and below has the function but gives annoying message "This function is unimplemented yet" so technically its not an API change — its a bug fix.

Thanks, Regina

[nicklas]

Yes, you are right, it includes st_max_distance too. Maybe you can put it in the description. I don't think I can. /Nicklas