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fix DISTINCT for Oracle databases #2935

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fix DISTINCT for Oracle databases #2935

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7813d2f
fix DISTINCT for Oracle databases
trollknurr May 14, 2015
c47ec60
no need to do distinct on every loop cycle & add analogue of distinct…
trollknurr May 14, 2015
de95598
removed using `view.model.objects`
trollknurr May 15, 2015
0906bf2
fix empty and_query
trollknurr May 15, 2015
745d8d0
added comment
Jun 3, 2015
e8b23c4
thin logic
Jun 25, 2015
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14 changes: 11 additions & 3 deletions rest_framework/filters.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
from django.core.exceptions import ImproperlyConfigured
from django.db import models
from django.utils import six
from django.conf import settings
from rest_framework.compat import django_filters, guardian, get_model_name
from rest_framework.settings import api_settings
from functools import reduce
Expand Down Expand Up @@ -100,12 +101,19 @@ def filter_queryset(self, request, queryset, view):

orm_lookups = [self.construct_search(six.text_type(search_field))
for search_field in search_fields]

and_queries = []
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Not sure I understand the motivation here - feels more obscure after this change rather than more clear.

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I don't sure, if calling queryset.filter(pk_in=set(pk_list)) will make duplications go away, as they pk still will be in pk_list. I want to filter original queryset by pk_list.
When we call filter with multiple kwargs or several times on one queryset it is equal to logical and.

for search_term in self.get_search_terms(request):
or_queries = [models.Q(**{orm_lookup: search_term})
for orm_lookup in orm_lookups]
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I'd prefer it if we didn't introduce the and_queries. We should keep each pull request as absolutely minimal as possible. Seems like there's two different changes here - the Oracle support as one, and the change in the filtering style as another. Let's just adopt the first of those two.
Apologies for the slow progress on this, but thanks for getting it nearly there! :)

queryset = queryset.filter(reduce(operator.or_, or_queries)).distinct()

and_queries.append(reduce(operator.or_, or_queries))

if and_queries:
# According to Oracle DB limits there is no capability to make a DISTINT on *LOB
if settings.DATABASES[queryset.db]["ENGINE"] == "django.db.backends.oracle":
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We'll want a brief comment here regarding needing this behavior for oracle and distinct.

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@tomchristie According to Oracle DB limits there is no capability to make a DISTINT on *LOB. There is a need to use SearchFilter with TextField (for example). That's why i pull this workaround for Oracle.

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Clarification: I was meaning that we should have a code comment for this.

pk_list = queryset.filter(reduce(operator.and_, and_queries)).values_list('pk', flat=True)
return queryset.filter(pk__in=frozenset(pk_list))
else:
return queryset.filter(reduce(operator.and_, and_queries)).distinct()
return queryset


Expand Down