#28062: Using QuerySet.iterator() with pgBouncer leads to nonexistent cursor
errors
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Reporter: Sergey Fursov | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Sergey Fursov):
Hi Josh,
> For your particular setup, I'd maybe recommend running a second
pgbouncer in session mode (or not use pgbouncer), and for queries that use
.iterator(), using that specific connection. As long as iterator() isn't
used in the majority of your requests, the number of connections shouldn't
spike too high.
This is reasonable suggestion, thanks
> We could also add an argument to .iterator() that allows users to opt-in
to the new server side cursors. We'd need to document the limitations, and
suggest ideal scenarios (use transaction.atomic, or
.using('non_pgbouncer_transaction_connection')).
This sound like the best option for me (at least compared to reverting
changes)
Another my point was the fact, that django use iterator internally in
ModelChoiceField for optimizing iteration over queryset and in several
serializer methods.
For my particular case it would be enough to add additional
ModelChoiceIterator to override default ModelChoiceField.iterator field
(we don't use DB serialization much, so i don't know, does serialization
part have big impact on production using). But i think this point should
be considered while working on this issue, too, because it might break
apps in production.
--
Ticket URL: <https://code.djangoproject.com/ticket/28062#comment:4>
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