Help by query - Mailing list pgsql-novice

Hello list.

I have the following problem:

Example table Origin

id   | length  |  source  |  target

1        25          33           45
2       100         45           60
3        12          22           11
4        78          60           55
5        20          24           60

Example Results: new table

id   | length  |  source  |  target | group | total length

1        25          33           45        1          145
2       100         45           70        1          145
3        12          22           11        3           12
4        78          60           55        2           98
5        20          24           60        2           98
6        20          30           70        1          145

Example Number variable      >= 150

and I want to create groups of elements on two conditions.

source or target must match, since this indicates that touch

to group items with the first condition and that the sum of its length does not exceed a given number

not be repeated elements in groups (The items can not be processed and reprocessed)

Can someone help?

Thanks in advance

regards
Mario