We have a proof of concept for nested sets in the /examples folder. However what I cant figure out with nested sets is, how do I load only the immediate children of a node ? That is the most common accessor I'd like on a self referential node and I'm not aware of how to do it. It makes it sort of impossible for there to be a ".children" accessor on a node, unless you load the full subtree and organize.
On Jan 18, 2009, at 1:33 PM, Kless wrote: > > SQA recommends the adjacency list pattern [1] over another patterns: > > "Despite what many online articles say about modified preorder, the > adjacency list model is probably the most appropriate pattern for the > large majority of hierarchical storage needs, for reasons of > concurrency, reduced complexity, and that modified preorder has little > advantage over an application which can fully load subtrees into the > application space." > > But should be in mind that it's slow in reads (althought it's fast in > writes). In change, the nested sets have very efficient reads at the > cost of high maintenance on write/delete operations. > > If any is interested in tree structures, there is an excelent > implementation for django ORM, django-treebeard [2], which has > included any benchmarks where you can see the reading differences > between different structures. > > > [1] > http://www.sqlalchemy.org/docs/05/mappers.html#adjacency-list-relationships > [2] http://code.google.com/p/django-treebeard/ > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
