Re: Trees in SQL

On Fri, 24 May 2002, Gregory Brauer wrote:

I have exactly the same situation.

Some work (argued to have better performance than Celko's implementation)
has been done by Miguel Sofer. (see http://www.utdt.edu/~mig/trees.tar.gz)

One fast solution would be using pgsql arrays and the contrib/array 
package.

However Oleg's and Theodor's contrib/tree solution looks the most 
attractive.

I will ask my wife today to do a translation of the doc,
(hoping russian and yugoslavian are alike :)

> 
> I hope this isn't an overly broad topic that ends up diverging into graph
> theory, but I have a tree structure of identical items (analogous to a
> filesystem directory tree) that I need to store in Postgres.  The
> "obvious" design is to give the table that will represent these objects
> a field identifying its "parent" that is a relation to the same table.
> However, this seems to make many common SQL queries rather difficult.
> 
> What sort of strategies are best for storing tree structures in a
> relational database, and how would one structure SQL queries to find,
> say, "all of the children anywhere under this node", or to represent
> the condition "if this node is a child at any depth under this other
> node"?  Are there good strategies for preventing cycles?
> 
> I'd appreciate any insights anyone can give.
> 
> Thanks.
> 
> Greg Brauer
> greg@wildbrain.com
> 
> 
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