[topology] ValidateTopology takes way too much time

[strk]

It's been running overnight (circa 7 hours now) w/out completing.

This is a topology with 33921 edges (total 314179 points), 26847 nodes and 12109 faces.

Haven't checked, but I bet it's the final checks for FACE/FACE overlap and FACE/FACE containment. There was a TODO in the code already about giving it more thoughts...

[strk]

So, removing the check for overlapping faces and face-in-face makes the run complete in 7 minutes against a reduced topology which wasn't completing in over 6 hours.

This other, smaller topology has these characteristics:

• 4896 nodes
• 5687 edges (total 87222 points)postgis make collection
• 1724 faces

Interesting enough, the validation reports lots of coincident nodes and an edge/edge crossing, which makes me wonder if it makes sense at all to try at analize faces if there are errors with edges (since faces are defined _by_ edges...)

[strk]

Oh, wait... running the validation again takes 2.7 seconds !! I wonder if the first run was done before some kind of auto vacuum analyze !

Subsequent runs keep taking 2.7 secs..

[strk]

As of r6658 the smaller topology validation takes 26 seconds (while it used not to complete in an hour). Considering fixed for now.

[strk]

Oh, the bigger topology just finished in 4 minutes and 15 seconds