#6785: QuerySet.get() should only attempt to fetch a limited number of rows
-------------------------------------+-------------------------------------
Reporter: deadwisdom | Owner: nobody
Type: | Status: new
Cleanup/optimization | Version: master
Component: Database layer | Resolution:
(models, ORM) | Triage Stage: Accepted
Severity: Normal | Needs documentation: 0
Keywords: | Patch needs improvement: 0
Has patch: 1 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
-------------------------------------+-------------------------------------
Comment (by shai):
Replying to [comment:8 akaariai]:
> Limiting the fetches doesn't work that well on most core databases.
[...] [T]he overhead of generating all the rows in the database and
transferring the results would still be there.
>
> To get rid of clone() overhead we could just call query.set_limits()
manually.
>
> With this all being said... I guess we are optimizing the wrong case
here. Successful .get() (just one row returned) should be optimized, not
the error case. I am not sure how much overhead LIMIT (or the nested
selects on Oracle) cost.
The intent of re-opening is exactly to optimize the successful case; the
issue is that the current implementation imposes an overhead on all
`get()` calls for better handling of the error case. Doing it with fetches
alone will remove this overhead -- for the successful case, asking for 21
results or for all results would be the same. I am not sure about the
added performance costs either, except that (as noted) the nested selects
on Oracle cost us in functionality.
On a side note, if more than one row is returned from the database, no
model instance at all needs to be created.
--
Ticket URL: <https://code.djangoproject.com/ticket/6785#comment:9>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/068.23aca87697a4b8dd7efa5161eadc5aeb%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
