v.patch: category abuse

[hamish]

Hi,

I am trying to patch together a couple hundred individual lines into a single map. Each line has been given a unique category number so that when their (identical) tables are merged they will not conflict.

after creating an empty vector with v.in.ascii and creating a matching table for it, the patch loop looks like this:

for MAP in `g.mlist vect pattern="track_*"` ; do
   v.patch -a -e in="$MAP" out=tracks --overwrite --quiet
done

g.mlist+v.db.select for some input maps:

cat|filename
10101|M02-001-0101
10224|M02-001-0224
10346|M02-001-0346
12305|M02-001-2305
20044|M02-002-0044
20209|M02-002-0209
20333|M02-002-0333
20458|M02-002-0458
20650|M02-002-0650
20813|M02-002-0813
20944|M02-002-0944
21112|M02-002-1112
21253|M02-002-1253
21434|M03-002-1434
21557|M03-002-1557
21721|M03-002-1721
21854|M03-002-1854

v.db.select for v.patch output:

cat|filename
10102|M02-001-0101
20327|M02-001-0224
30674|M02-001-0346
42980|M02-001-2305
63025|M02-002-0044
83235|M02-002-0209
103569|M02-002-0333
124028|M02-002-0458
144679|M02-002-0650
165493|M02-002-0813
186438|M02-002-0944
207551|M02-002-1112
228805|M02-002-1253
250240|M03-002-1434
271798|M03-002-1557
293520|M03-002-1721
315375|M03-002-1854

you can see that the category value in the output patch becomes:

 1 + map1
 1 + map1 + 1 + map2
 1 + map1 + 1 + map2 + 1 + map3
 .
 .
 .

how to make max_cat() or what ever is doing it stop?

• I cannot guarantee that input maps arrive sorted by cat, smallest to largest.
• It has to check if the cat is already used, if so it has to decide what to do with existing database attributes. Probably exit with a fatal error.
• I suppose this needs a flag: you either care to preserve the cat but accept fatal errors and a small time penalty; or you don't mind reassigning cats to avoid fatal errors.

thanks, Hamish

[hamish]

if the attribute table is not being copied (the -e flag is not used) then allowing duplicate cats is in fact wanted. again a flag could be used to avoid duplicates if that's what the user wants.