On Sat, Aug 25, 2012 at 12:35 PM, Anssi Kääriäinen <[email protected]>wrote:
> I have done some more ORM refactoring work. I thought it would be a > good idea to post a summary of what is going on. > > First, I haven't committed the utils.tree refactoring patch I was > planning to commit [https://github.com/akaariai/django/commits/ > refactor_utils_tree]. The reason is that I now feel that add_filter() > and deeper levels of the Query class need some refactorings first. > > There is some work going on in the refactoring of the deeper levels of > the ORM. I committed join promotion improvement patch today: [https:// > code.djangoproject.com/ticket/16715#comment:25]. I have more planned > improvements to commit: > > > * Remove "dupe avoidance" logic from the ORM (#18748). > This is removing some code I strongly believe isn't needed any more. > This is still pending Malcolm's review. > > * Fix join promotion in disjunctive filters (#18854). > This one should make join promotion in disjunction cases cleaner and > more efficient (as in less OUTER JOINS). In addition, this will make > add_q/add_filter a bit easier to understand. The problem currently is > that the first ORed filter is added to the query with connector=AND, > the rest of the filters in the disjunction with connector=OR. This is > done for join promotion reasons. However, this is very confusing when > trying to work with add_q and add_filter, and doesn't actually work > that well (see the added tests in the ticket's patch). > > * Remove "trim" argument from add_filter (#18816). > The trim argument is only needed for split_exclude (that is, pushing > negated m2m filters to subqueries). So, add_filter (and then also > trim_joins) needs to handle split_exclude's special case. Handling > this case inside split_exclude() turned out to be a little ugly, but > IMO less ugly than the trim flag. This also allows further cleanups in > the following item. > > * A biggie: complete refactoring of setup_joins (#10790, a separate > ticket could be good for this). > Best described in the last post in the ticket [https:// > code.djangoproject.com/ticket/10790#comment:41]. The patch isn't > completely ready (there are still stale comments floating around, the > commit history is ugly). > > > Applying the above patches should make the ORM code easier to follow. > Further features like custom lookups should be easier to add. The > produced queries should be of higher quality (less joins, less left > joins). And, it should be easier to do cleanups in the ORM. > > A note about extra_filters: The setup_joins() refactoring removes the > "extra_filters" system used for generic relations. The system adds new > filters to the query for any joins generated by generic relations. > However, these are pushed into the WHERE clause, and this doesn't work > nicely with LOUTER JOINS. The refactoring adds the extra condition > directly into the join's ON clause, thus producing correct left outer > join conditions. > > The extra_filters is (as far as I know) private API, but I'd like to > know if this is heavily used by the community. If so, it is easy > enough to leave this API in place (while still fixing the generic > relations stuff). > > I hope I can get reviews for the above tickets. Getting reviews from > people who do not know the ORM is valuable, too, as one of the goals > is to make the ORM easier to understand. As the author I can't easily > see if my attempts to make the code easier to follow actually improve > anything. > > Even if I do not get any reviews, I think it is a good idea to push > these patches in. Thus far it has been hard to get reviews for larger > ORM patches, and I am afraid that the refactoring work will stall if I > have to wait for a full review for every patch. If you want to review > the patches, but don't have time just now, please make a note in the > tickets about this. There is no hurry. > > If pushing these patches without reviews seems like a bad idea to you, > then please say so (preferably before I commit anything)... > > I am sorry if I haven't worked on other patches I thought I had time > to work on. The core ORM refactorings are IMO really important to work > on, and thus they have bypassed some other items in my admittedly too > long TODO list. > > - Anssi > > -- > You received this message because you are subscribed to the Google Groups > "Django developers" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/django-developers?hl=en. > > Anssi, Thanks for all your awesome work on this, of the patches I've reviewed so far they've been really good. I don't think I'll have time to review until DjangoCon, so feel free to either commit now or wait, whichever you'd prefer! Alex -- "I disapprove of what you say, but I will defend to the death your right to say it." -- Evelyn Beatrice Hall (summarizing Voltaire) "The people's good is the highest law." -- Cicero -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
