Re: Recommended modules for Parent-Child trees?

[tilly]

If you wish the nodes to be stored in a database, then I'd suggest reading (and understanding) Nested Set Trees. In the common case of insert occasionally, query often, they are far more efficient than the usual adjacency model that people think of.

Unfortunately I don't know of a module that automates generating them in Perl, and I'm not entirely sure what such a module should look like. (Which may be why I don't know of one...) So you'd have to do some reinvention, but at least you'd reinvent a good version.

[Hero Zzyzzx]

Got it. Nested set trees are very, very cool. Wow! Thanks for that. The efficiency with which you could select siblings/parents/ancestors and subtrees is crazy, recursive queries always bugged me (I've implemented parent-child relationships before).

It's a bit hard to wrap my head around how to get it into code, but I can probably come up with something given the SQL in the article.

I need to figure out now if speed of execution outweighs speed of development, and figure out where I'm going to spend my time.

[stvn]

Hero Zzyzzx

Here is another article by the same author (actually it somwhat seems to be a longer version of the same). You have to scroll through the first sections of each article to get to the "Tree's in SQL" stuff.

Part one of the article ...

http://www.dbmsmag.com/9603d06.html

Then part two of the article ...

http://www.dbmsmag.com/9604d06.html

and the third part ...

http://www.dbmsmag.com/9605d06.html

Enjoy.

[Hero Zzyzzx]

Jeez. 1996 that thing was written. Almost makes me wish I had a computer science degree. Besides complexity (like that's something to put aside) a nested set tree model really seems the way to go in my case.

I fear my hubris is getting the best of me, but I think I'm going to be writing a new DBI-backed module. . .