Re: Processing Tables containing tree-like data

[Michael Glaesemann <grzm(at)seespotcode(dot)net>]

On May 29, 2007, at 11:58 , psql-novice(at)netzach(dot)co(dot)il wrote:

> I have a table which looks like this:
>
> id	info	parentid
> 0	<God>	0
> 1	Adam	0
> 2	Cain	1
> 3	Abel	1
> 4	Seth	1
> 5	Enosh	4
> ....
>
>
>
> I am looking for a fast and efficient way of finding ALL the  
> descendents
> of any particular node, to unlimited depth.
>
> Is there a standard database trick for doing this efficiently ?  
> Writing
> a recursive function would be extremely inefficient for repeated
> queries.

What you've got there is often called an adjacency list. Check out  
the connect_by function in the tablefunc contrib module (contrib/ 
tablefunc). You might also want to google for SQL nested sets to find  
an alternative method of doing handling trees.

Michael Glaesemann
grzm seespotcode net