Re: contrib/tree issues

On Wed, 29 May 2002, Oleg Bartunov wrote:

> > How can we find  "maximum" direct child of a node?
> >
> > dynatree=#
> >
> > Now we find the children of '1' of level 2:
> >
> > dynatree=# SELECT node from achtree where node <* '1.*.0';
> >  node
> > ------
> >  1.1
> >  1.2
> > (2 rows)
> >
> > dynatree=#
> >
> > Now if we want to insert another level 2 child of '1',
> > how can we get the current maximum value of level 2 children of node '1'??
> > (in this case 2), so that we can insert '1.3' to the table???
> 
> 
> Just use functions entree_next(entree), bitree_next(bitree) -
>  return next free node.

Ok, entree_next(1.2) is fine, but how can we know this particular
1.2 ^
??

Think of a sequence for example that increments itself.

Now, if we have a unique index on a entree column, how can we guarantie
the next one will be the previous max child + 1??

> 
> 
> 
> 
> >
> > Also, i want to ask if somebody has extended postgresql's jdbc
> > implemantation to include support for bitrees,entrees.
> >
> > One maybe slow solution for both of the above would be to
> > be able to cast e.g. entree to text, so that
> >
> > a) taking the lexicographically maximum bitree value would give the
> > maximum current child, and
> > b) java intergration would be trivial through java.lang.String.
> >
> > Thanx
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 3: if posting/reading through Usenet, please send an appropriate
> > subscribe-nomail command to majordomo@postgresql.org so that your
> > message can get through to the mailing list cleanly
> >
> 
>     Regards,
>         Oleg
> _____________________________________________________________
> Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> Sternberg Astronomical Institute, Moscow University (Russia)
> Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
> phone: +007(095)939-16-83, +007(095)939-23-83
> 

-- 
Achilleus Mantzios
S/W Engineer
IT dept
Dynacom Tankers Mngmt
tel:    +30-10-8981112
fax:    +30-10-8981877
email:  achill@matrix.gatewaynet.com       mantzios@softlab.ece.ntua.gr