Opened 12 years ago
Closed 8 years ago
#18729 closed Bug (fixed)
Admin changelist view defaults to `DISTINCT`, unusable on reasonably sized databases
Reported by: | Henrique C. Alves | Owned by: | AlexMalek |
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Component: | contrib.admin | Version: | dev |
Severity: | Normal | Keywords: | admin sql distinct slow performance |
Cc: | Triage Stage: | Accepted | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
The default behavior on the admin is not usable for reasonably sized tables (a couple thousand tuples is enough for >1s queries).
Right now, it always includes a DISTINCT
clause if you add a M2M field on list_filter
, even if you're not applying any filters. Use of DISTINCT
is known to be painfully slow, and even more so without a WHERE
clause, because it forces SQL databases into a full table scan. The behavior is not easily overridden because the logic is scattered on a couple ChangeList
methods (https://github.com/django/django/blob/master/django/contrib/admin/views/main.py#L299).
The only solution right now is not including a M2M field on list_filter
and limiting functionality. It would be better if that behavior could be overridden (a use_distinct
parameter on get_query_set
?) or, optimally, moving this logic somewhere else. Ticket #15819 already includes a patch for that.
Change History (9)
comment:1 by , 12 years ago
Resolution: | → duplicate |
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Status: | new → closed |
Type: | Uncategorized → Bug |
comment:2 by , 11 years ago
Resolution: | duplicate |
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Status: | closed → new |
I think it is a different issue.
It is possible to alter the check that examines list_filter to determine if distinct() is needed based on if the field appears in the query/request but this does not address the deeper issues in #15819
For example in Django 1.5.2 I think the following changes solves the issue:
django/contrib/admin/util.py: 20c20 < def lookup_needs_distinct(opts, lookup_path, query_dict=None): --- > def lookup_needs_distinct(opts, lookup_path): 29,31c29 < not field.field.unique) and < (query_dict is None or (field_name in ",".join(query_dict.keys()))) < ): --- > not field.field.unique)): django/contrib/admin/views/main.py: 128c128 < field_path, lookup_params)) --- > field_path))
comment:3 by , 10 years ago
Owner: | changed from | to
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Status: | new → assigned |
comment:5 by , 10 years ago
Triage Stage: | Unreviewed → Accepted |
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comment:6 by , 10 years ago
Triage Stage: | Accepted → Ready for checkin |
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comment:7 by , 10 years ago
Patch needs improvement: | set |
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Triage Stage: | Ready for checkin → Accepted |
I left comments for improvement on the PR. Please uncheck "Patch needs improvement" when you update it, thanks.
Resolving this as a dupe #15819. Looks like that issue has all of the same points here and fixes this issue.
Feel free to re-open if I missed something in this ticket that's different than #15819.