#6785: QuerySet.get() should only attempt to fetch a limited number of rows
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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 |
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Comment (by akaariai):
Limiting the fetches doesn't work that well on most core databases. If I
recall correctly sqlite, postgresql and mysql all do transfer all of the
rows of the query when accessing the results (for PostgreSQL I know this
is the case). So, while limiting the fetches would result in less model
instances being generated, the 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.
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Ticket URL: <https://code.djangoproject.com/ticket/6785#comment:8>
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