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 -~----------~----~----~----~------~----~------~--~---
