spacedman wrote: > If you can rework your database slightly you can use Modified Preorder > Tree Traversal, which is a really slick way of doing trees in > relational databases. You can get everything you need to know to > present a tree diagram with ONE database call. If you store parent-id > then you can end up hitting the database many many more times as you > climb up and down the tree. > > See > http://code.djangoproject.com/wiki/ModifiedPreorderTreeTraversal > > And > http://www.sitepoint.com/print/hierarchical-data-database > > It takes a bit of thinking about, but once it 'clicks' you'll see how > neat it is. > > Barry
When I've dealt with large trees in a web application, a big part of the problem has been in sending the structure of the entire tree back to the client. In that situation we retrieved the top-level nodes only, and expanded nodes for a specific parent only when requested. This was trivial with the naive parent_id approach. I can't see any way of doing this with MPTT - Is there any way in this storage method to get the children of a node without also getting all descendants? I guess you could store both the l/r values and parent_id - but that's less than ideal. Thanks - I hadn't seen the MPTT method before. It looks to be useful, in the right circumstances. Cheers, xtian --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users -~----------~----~----~----~------~----~------~--~---
