AFAICT the performance hit is minimal unless you are doing something slow when logging warnings (e.g. -Walways with a slow I/O py.warnings handler).
The Python/Django instrumentation simply adds a value to Model._state and look it up on attribute accesses. Cheers, Simon Le lundi 20 août 2018 19:34:11 UTC-4, Curtis Maloney a écrit : > > In general this sounds like a tremendously useful tool... I'm caused to > wonder, however... what, if any, are the performance impacts? > > -- > Curtis > > > > On 08/21/2018 08:10 AM, charettes wrote: > > Regarding the lazy loading of deferred fields and foreign keys > > I wanted to mention I've been working on a third-party application > > that allows overriding the default behavior[0]. > > > > The project works by tainting objects retrieved from "sealed" > > querysets and having fields descriptors lookup whether or not > > the object is "sealed" on attribute access and warn the developer > > about it if it's the case. Warnings can be elevated to errors > > using `filterwarnings` when deemed appropriated (e.g. CI, staging). > > > > It has been an useful tool to assist in figuring out where > > `select_related()` and `prefetch_related()` should be used > > to adjust complex projects database interactions. > > > > I assume a similar pattern could be used to mark objects retrieved > > from `QuerySet.__aiter__` to prevent non-async queries from being > > performed on attribute accesses; on `Model._state.async = True` > > field descriptors would error out. > > > > > > Cheers, > > Simon > > > > P.-S. > > > > While the project might look complex most of the code takes care > > of the delicate tasks of replacing fields descriptors once models > > are configured which could be significantly simplified if it was > > part of Django core. > > > > [0] https://github.com/charettes/django-seal > > Le samedi 9 juin 2018 02:30:59 UTC-4, Josh Smeaton a écrit : > > > > I think most of what you've laid out sounds great and that pursuing > > async Django is in the projects best interests. The sync to async > > and async to sync wrappers that have come out of channels give me > > much more confidence that this project is doable in a reasonable > > amount of time with backwards compatibility being preserved. > > > > The only real concern I have at the moment is around your comments > > regarding on demand foreign key traversal. If existing code running > > synchronously is going to be impacted, that's going to be very > > difficult for a lot of people. If it's only asynchronous traversal > > that'll have issues, then I have no real concern, as on demand > > foreign key fetching is usually a bug anyway. > > > > Having a brief read through the psycopg asynchronous docs[0], it > > looks like a number of features will be impossible or troublesome to > > use, like transactions, executemany, and named cursors (.iterator() > > with server side cursors). We'd also need to investigate how > > pgbouncer would work in async mode, as most large sites using > > postgres are also using pgbouncer. I would expect support can only > > further improve, especially if there is a driver like django > > pushing. Fallback would just be to run inside a thread pool though, > > so it's not a blocker for the rest of the proposal. > > > > Very exciting times ahead! > > > > [0] http://initd.org/psycopg/docs/advanced.html#asynchronous-support > > <http://initd.org/psycopg/docs/advanced.html#asynchronous-support> > > > > On Monday, 4 June 2018 23:18:23 UTC+10, Andrew Godwin wrote: > > > > Hello everyone, > > > > For a while now I have been working on potential plans for > > making Django async-capable, and I finally have a plan I am > > reasonably happy with and which I think we can actually do. > > > > This proposed roadmap, in its great length, is here: > > > > https://www.aeracode.org/2018/06/04/django-async-roadmap/ > > <https://www.aeracode.org/2018/06/04/django-async-roadmap/> > > > > I'd like to invite discussion on this potential plan - > including: > > > > - Do we think async is worth going after? Note that this is > > just async HTTP capability, not WebSockets (that would remain in > > Channels) > > > > - Can we do this in a reasonable timeframe? If not, is there a > > way around that? > > > > - Are the proposed modifications to how Django runs sensible? > > > > - How should we fund this? > > > > There's many more potential questions, and I really would love > > feedback on this. I'm personally pretty convinced that we can > > and should do this, but this is a decision we cannot take > > lightly, and I would love to hear what you have to say. > > > > Andrew > > > > -- > > 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 django-develop...@googlegroups.com <javascript:> > > <mailto:django-developers+unsubscr...@googlegroups.com <javascript:>>. > > To post to this group, send email to django-d...@googlegroups.com > <javascript:> > > <mailto:django-d...@googlegroups.com <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/0b3b92b9-eee7-4909-82d6-c0138e8b5760%40googlegroups.com > > > < > https://groups.google.com/d/msgid/django-developers/0b3b92b9-eee7-4909-82d6-c0138e8b5760%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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