mptt

问题 Conditions: Django==1.8.7 и django-mptt==0.8.0. There is a model: class Tree(mptt_models.MPTTModel): name = models.CharField(max_length=120, unique=True) slug = models.SlugField(max_length=256, unique=True) parent = mptt_models.TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True) class MPTTMeta: order_insertion_by = ['name'] I can fill it with admin interface and show on a site pages. I can fill it with django shell: Python 2.7.3 (default, Jun 22 2015, 19:43

问题 I have: Home Things with Fur Dog Horse Basket Ball Games Twenty One Horse Assuming the slug for each is title.lower().replace(' ', '-') , my URLs would be: /home/ /home/things-with-fur/ /home/things-with-fur/dog/ /home/things-with-fur/horse/ /home/basket-ball-games/ /home/basket-ball-games/twenty-one/ /home/basket-ball-games/horse/ The slug field is unique_together with the parent . I need to, based on the URL segements, query for the correct category. I can't simply query for the basket ball

问题 I have a table in my database where I store a tree structure using the hybrid Nested Set (MPTT) model (the one which has lft and rght values) and the Adjacency List model (storing parent_id on each node). my_table (id, parent_id, lft, rght, alias) This question doesn't relate to any of the MPTT aspects of the tree but I thought I'd leave it in in case anyone had a good idea about how to leverage that. I want to convert a path of aliases to a specific node. For example: "users.admins.nickf"

问题 I'm trying to make a model for categorizing some objects. I already tried using django-mptt to easily retrieve related categories, and now I'm searching different solutions to find the best one. I can't find out though what are main differences between Materialized Path, Adjacency List and Nested Set. Wikipedia didn't give me a short answer, all I know is mptt is probably Nested Set... Can anyone explain it to me in few words ? 回答1: It's easier to explain with examples than with a few words.

问题 Does anybody have an efficient algorithm to retrieve all ancestors of an mptt queryset? The best I could think of so far is something like this: def qs_ancestors(queryset): if isinstance(queryset, EmptyQuerySet): return queryset queryset_aggs = queryset.values_list('tree_id', 'level').annotate(max_lft=Max('lft'), min_rght=Min('rght')) new_queryset = queryset.none() for tree_id, level, max_lft, min_rght in queryset_aggs: ancestors = MyModel.objects.filter( tree_id=tree_id, level__lt=level, lft

问题 I have the following self-join query: SELECT A.id FROM mytbl AS A LEFT JOIN mytbl AS B ON (A.lft BETWEEN B.lft AND B.rgt) The query is quite slow, and after looking at the execution plan the cause appears to be a full table scan in the JOIN. The table has only 500 rows, and suspecting this to be the issue I increased it to 100,000 rows in order to see if it made a difference to the optimizer's selection. It did not, with 100k rows it was still doing a full table scan. My next step was to try

问题 I have a multidimendional array that I want to transform to a Modified Pre-order Traversal Tree: $data = array( "MTGO" => array("Magic Online" => array("MTGO Masters Edition", "MTGO Masters Edition II", "MTGO Masters Edition III", "MTGO Masters Edition IV")), "Expansions" => array("Ice Age Cycle" => array("Coldsnap Theme Decks", "Ice Age", "Alliances"), "Theros" => array("Theros")), "unclassified" => array("Portal", "Eight Edition") ); I've tried by looping through the nested arrays, or using

问题 I'm trying to get all the children of a category: def list_sub(self, category_name): # this will return the parent if exists category = Category.objects.filter(seo_title__exact = seo_title).filter(lang__exact = 'pt-PT').filter(level__exact = 1) if category: # but this doesn't work and in the documentation there are no examples # of how to get it. See link about the method sub_categories = category.get_children() http://django-mptt.github.com/django-mptt/models.html#get-children Update1: qc =

问题 I am having problem implementing django mptt. Here is my model: class Company(models.Model): name = models.CharField( max_length=100) parent = models.ForeignKey('self', null=True, blank=True, related_name='children') mptt.register(Company, order_insertion_by=['name']) And class Financials(models.Model): company = models.ForeignKey(Company, related_name="financials") year = models.IntegerField() revenue = models.DecimalField(max_digits = 10, decimal_places = 2) So what I am looking at is how

问题 My first post here! Seems like this is the place to get wise ;) I am currently in the middle of some testing with my first ever attempt to try the MPTT (Modified Preorder Tree Traversal) approach to storing data in my Mysql database with the help of PHP. However, I am trying to find out the most performance-oriented way to get all list elements on a specific level, with a specific parent. That could translate into getting the categories Saab and Chrysler from the image below, if the parent