Re: Proposal of hierarchical queries, a la Oracle

Evgen,

read info about ltree module
http://www.sai.msu.su/~megera/postgres/gist/ltree/

Do you have implemented indexed access ?

regards,

Oleg

On Sat, 16 Nov 2002, Evgen Potemkin wrote:

> I was have made a module like ltree, i don't know how you implement it,
> but mine doesn't fit.
>
> The problem : for ex. you need to select a tree, but with childs of
> each parent is sorted.
> in my module i've defined a tree path as set of
> numbers separated by dot ('1.234.456.789'::hier for ex.), a comparision
> operators <,>,<=,<=,= , operators for checking for ancestors/descedants
> <<,>>,<<=,>>=.
> create table t (field text, node::hier);
> then i do "select field from t where where node <<'1' order by node";
> 'order by' - for tuples being in order of tree (first is root,then first
> child, then first child of first child, .. so on). works perfectly well.
>
> THE MATTER OF PROBLEM:
> tuples can't be sorted alphabetically by 'field', because of 'order by node'
> clause. 'order by node,field' doesn't really work because 'node' is first
> key, if 'order by field,node' - then we don't get a tree.
>
> if i do nodes on one level is equal, then childs of one node in some cases
> are migrate to another node of same level :) as far as i understand problem
> is in pg's sort. it's not a bug but feature of sort alghorithm.
>
> The minor problem is that such tree a bit difficult to maintain. for ex. if i need
> to move some node to elsewhere in tree, i need to update all childs, sub
> childs, ... of this node.
>
> regards
> ---
> .evgen
>
> On Fri, 15 Nov 2002, Oleg Bartunov wrote:
>
> > Evgen,
> >
> > you'd need to post your message and patch to hackers mailing list.
> > btw, did you try contrib/ltree module ?
> >
>
> > 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
> >
> >
>

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