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
> >
> >
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> >
>
> Regards,
> Oleg
> _____________________________________________________________
> Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> Sternberg Astronomical Institute, Moscow University (Russia)
> Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
> phone: +007(095)939-16-83, +007(095)939-23-83
>

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