Opened 6 years ago

Closed 5 years ago

#29429 closed Bug (needsinfo)

Make len lookup for ArrayField use the array_length function

Reported by: creative3000 Owned by:
Component: contrib.postgres Version: 2.0
Severity: Normal Keywords: db orm ArrayField postgres
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description (last modified by creative3000)

When you filter by len like in documentation example:

  Post.objects.filter(tags__len=1)

But if you try to annotate something an error pops up example:

 Post.objects.all().annotate(tag_len=F('tags__len'))

It really seems that it should work by default, but instead I needed to use something like this 

 Post.objects.all().annotate(tag_len=Func(F('tags'), 1, function='array_length'))

Change History (5)

comment:1 by creative3000, 6 years ago

Description: modified (diff)

comment:2 by creative3000, 6 years ago

Description: modified (diff)
Owner: changed from nobody to creative3000
Status: new → assigned

comment:3 by Tim Graham, 6 years ago

Component: Database layer (models, ORM) → contrib.postgres
Easy pickings: unset
Summary: Postgres ArrayField doesn't work properly. → Make len lookup for ArrayField use the array_length function
Triage Stage: Unreviewed → Accepted

I haven't dug into this. It might be fine. Accepting for further investigation.

comment:4 by creative3000, 6 years ago

Owner: creative3000 removed
Status: assigned → new

comment:5 by Claude Paroz, 5 years ago

Resolution: → needsinfo
Status: new → closed

Are you sure the line Post.objects.all().annotate(tag_len=F('tags__len')) is valid?
Where did you read in the documentation a similar construct with a Transform inside a F() expression?

In my opinion, you should have written:

from django.contrib.postgres.fields.array import ArrayLenTransform
Post.objects.all().annotate(tag_len=ArrayLenTransform('tags'))
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