CODEWITHSUNDEEP
pythondjangopostgresql
winsmith
winsmith

Reputation: 21562

Django QuerySets on PostgreSQL contain duplicate objects

This is Django 1.4.2 running on OSX, with a PostgreSQL database.

Here's my model:

class RideRequest(models.Model):
    user = models.ManyToManyField(User, related_name="ride_requests", symmetrical=False)
    status = models.IntegerField(choices=STATUS_CHOICES)

In all my filter calls for this model, I get all objects twice. 

[10]: queryset = RideRequest.objects.filter(id=8)
[11]: for q in queryset: print q.id
8
8

I just looked into the database, and every entry is only present once. Any ideas why this would happen? I can't easily switch to SQLite because of certain DB constraints.

Edit: Here's the raw SQL query output of RideRequest.objects.filter(id=8).query. It too returns two rows instead of the expected one. Could it be because of the excessive JOINing that is going on? 

SELECT "rides_riderequest"."id", "rides_riderequest"."ride_id", 
…
FROM "rides_riderequest" 
LEFT OUTER JOIN "rides_riderequest_ride_request_stations" 
ON ("rides_riderequest"."id" = "rides_riderequest_ride_request_stations"."riderequest_id")
LEFT OUTER JOIN "rides_riderequeststation" 
ON ("rides_riderequest_ride_request_stations"."riderequeststation_id" = 
"rides_riderequeststation"."id") WHERE "rides_riderequest"."id" = 8  
ORDER BY "rides_riderequeststation"."departure_time_min" DESC;

Upvotes: 0

Views: 498

Answers (1)

dani herrera
dani herrera

Reputation: 51645

I suspect that in model Meta section you have set model ordered by an 'external' field (related model 'station__departure_time'). When you write query django make joins to this 'external' field for sorting purposes.

In this case you should use distinct() method or clear ordering using .order_by()

Upvotes: 1

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