Hey Aymeric, Performace issues I experienced with date hierarchy are: 1. The query generated by the filter for the list view is not utilizing range indexs - I hope this PR will resolve this issue. 2. The date hierarchy template tag generate a list of distinct values for the hierarchy level - I solved this issue, as you mentioned above, by overriding the template tag and providing my own implementation <https://github.com/hakib/django-admin-lightweight-date-hierarchy#quickstart> (only past dates, all options etc). I found this old ticket <https://code.djangoproject.com/ticket/23242> which is still open - maybe we can revisit this as well.
Haki. On Saturday, December 16, 2017 at 6:28:51 PM UTC+2, Aymeric Augustin wrote: > > Hello Haki, > > Yes, I always found that SQL query weird, I think we can do better. > > I didn't review your implementation but I wanted to encourage you anyway > :-) > > This optimization matters for large tables. In that case, finding all the > years / months / days for which objects exist in the database may be more > expensive than selecting the objects to display. I believe others have > tried optimizing this by : > > - showing years between the min / max values, which are trivial to > determine with an index ; this works well when all your data was generated > during the lifetime of your service, so you have at most a few decades to > display, often less, and there's data for each year > - providing links for all possible months or days within a given year or > month respectively. > > While that optimization is very related to the one you're proposing, I > believe they're independent, you don't need to do both at once. > > Best regards, > > -- > Aymeric. > > > > On 16 Dec 2017, at 10:27, Haki Benita <[email protected] <javascript:>> > wrote: > > Hey, I'm a new member to this group and I would like to suggest > implementing a custom filter for date_hiearchy. > > The date_hierarchy filter is currently relying on the default filter > implementation by Django Admin. > > *I think we can use the heirarchical nature of the date hierarchy to > generate a better filter condition.* > > A URL generated by a the date hierarchy template tag might look like this: > admin/app/model?created__year=2017&created__month=12&created__day=16 > > The query generated by this URL will look like this (Postgresql): > where created between '2017-01-01' and '2017-31-12' and extract('month', > created) == 12 and extract('day', created) == 16; > > The problem with this condition is that it *uses databse functions to > filter the date which makes it very difficult for the database to utilize > range based indexes (such as btree). * > I'm sure many developers (me included) are adding btree indexes on the > date hierarchy field to support such queries but the generated filter > prevents the database from using them. > There are solutions outside of Django for this problem such as function > based indexes but those come at a cost which can easily be avoided. > > Another approach from within Django is to simplify the condition in a way > that the database can *better utilize range indexes:* > where created > '2017-12-16' and created < '2017-12-17'; > > I wrote about this problem in this blog post > <https://codeburst.io/django-admin-range-based-date-hierarchy-37955b12ea4e> > and implemented the above as a SimpleListFilter > <https://github.com/hakib/django-admin-lightweight-date-hierarchy/blob/master/django_admin_lightweight_date_hierarchy/admin.py#L47> > > in this package. > <https://github.com/hakib/django-admin-lightweight-date-hierarchy> > > To implement the simplified condition within Django I suggest adding the > following to ChangeList: > > - Identify date_heirarchy fields using the following pattern: > > re.compile(*r'^{}__(day|month|year)$'.format(self.date_hierarchy_field*)) > > > - In ChangeList.get_filters > <https://github.com/django/django/blob/master/django/contrib/admin/views/main.py#L137>, > > after applying the custom ListFilters and before applying the "default" > filtering on what's left; if date_hierarchy is defined for the model, > Identify the filters, apply a range based filter > <https://github.com/hakib/django-admin-lightweight-date-hierarchy/blob/master/django_admin_lightweight_date_hierarchy/admin.py#L10> > > and remove the values from the parameter list. > > *Other considerations* > > - This change is backward compatible. > - Will most likely improve performace of large list views with > date_heirarchy. > - The custom filter is applied after the ListFilters so projects that > implemented their own filters on date hierarchy fields will not be effected. > > Please let me know what you think and if there are other things I haven't > considered. > > Haki Benita. > > > > -- > You received this message because you are subscribed to the Google Groups > "Django developers (Contributions to Django itself)" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/django-developers. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/24ab9a20-cd8e-40c4-a257-3c8b4ee12fde%40googlegroups.com > > <https://groups.google.com/d/msgid/django-developers/24ab9a20-cd8e-40c4-a257-3c8b4ee12fde%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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