To: pgsql-sql@postgresql.org
From: Axel Straschil <axel@straschil.com>
Subject: How to store directory like structures?
Date: Sun, 3 Apr 2005 10:13:48 +0000 (UTC)
Lines: 30
Message-ID: <slrnd4vghu.tp.axel@m2.sine>
User-Agent: slrn/0.9.8.1 (Linux)

Hello!

I want to store some structure like:

CREATE TABLE node
(
	nodeid	SERIAL PRIMARY KEY,
	parent	INT REFERENCES node(nodeid)
			ON UPDATE CASCADE ON DELETE CASCADE,
	label	TEXT,
	UNIQUE (parent, label),
	...
	data 
	...
);

The label is used to map a node to a directory like strukture, so i can
have a function directory_for(nodeid) which gives me
/root_label/parent_label/parent_label/my_label (root labels have NULL as parent)

The problem is the ammount of queries when i've got deep nodes, and I
often have to query if a node is "in path" of another node.

Is there a good solution to build directory-tree like datastruktures?
I found, http://www.sai.msu.su/~megera/postgres/gist/ltree/ which seems
to do what i want, but I've no idea (and probalbly no chance) to get
that running on my system ;-(

Thanks,
AXEL.