take a look on contrib/ltree
On Wed, 26 Sep 2007, paul.dorman wrote:
> Hi everyone,
>
> I would like to know the best way to implement a DAG in PostgreSQL. I
> understand there has been some talk of recursive queries, and I'm
> wondering if there has been much progress on this.
>
> Are there any complete examples of DAGs which work with PostgreSQL? I
> would like to be able to do the following operations for a
> categorization system:
>
> 1. Given a node, get one or more field values out of every parent node
> 2. Given a parent node, get one or more field values out of every
> child node
> 3. Given two or more parent nodes, identify any common children.
>
> I do not need to determine shortest paths between parents and
> children, only to be able to iterate over them as efficiently as
> possible.
>
> I'd like to keep things dynamic so changes up the hierarchy don't
> require changes to any of the children (unless their direct parents
> are changed). I'd also like to keep as much processing as possible in
> the database to minimize the traffic between my application and the
> DB, so I think I'm looking for SQL and stored procedure solutions.
>
> Any pointers would be great, as I'm not a DBA and do not have the
> experience to make judgments about the best possible approach.
>
> Regards,
> Paul Dorman
>
>
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Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83