Avoid query explosion for related fields where I can user pk_only_opt…

[santiavenda2]

…imization.

Also, fix AutoPrefetchMixin for ReverseOneToOneDescriptors.

[sliverc]

I tested this change in on one of my projects and it works smoothly. Thanks.

It seems that in drf 3.1 _readable_fields doesn't exist so CI is failing. Not sure whether there is an alternative but I would be in favor of dropping support for 3.1 which is already more than 2.5 years old.

[santiavenda2]

@sliverc I have fixed the problem we had in DRF<3.2 (_readable_field property didn't exist on Serializer class)

I think the change is ready to be merged

[codecov-io]

Codecov Report

Merging #374 into master will decrease coverage by 0.4%.
The diff coverage is 57.5%.

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
- Coverage   92.37%   91.97%   -0.41%     
==========================================
  Files          56       56              
  Lines        2887     2917      +30     
==========================================
+ Hits         2667     2683      +16     
- Misses        220      234      +14

Impacted Files	Coverage Δ
example/views.py	90.74% <100%> (ø)	⬆️
rest_framework_json_api/utils.py	91.13% <100%> (ø)	⬆️
rest_framework_json_api/relations.py	82.95% <100%> (+0.19%)	⬆️
rest_framework_json_api/renderers.py	85.81% <41.66%> (-1.12%)	⬇️
rest_framework_json_api/serializers.py	80.62% <54.54%> (-4.16%)	⬇️

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[mblayman]

I'm going to re-target this PR to master since the main development branch is now over there.

[mblayman]

@santiavenda2 because this is now targeting master, there is a conflict on the branch. master dropped a bunch of supported Django version so I think that might provided an opportunity to simplify the PR code.

[santiavenda2]

@mblayman done

[mblayman]

Could you explain why this is overriding to_representation from the ModelSerializer? It seems like DJA is likely to diverge from the DRF upstream if this method is added. Is there some extra stuff added here that you could call out?

[aidanlister]

@mblayman this is returning the JSON API identifier of the object without diving down the recursive rabbit whole. It looks like an elegant solution.

[mblayman]

Thanks for the second look, @aidanlister. I took a look at the DRF implementation and the method seems small enough that it would be hard for DJA to diverge too much from upstream.

[aidanlister]

I've reviewed the PR and we're now testing this PR internally - everything seems to be working as expected - very impressive. Next step we'd do a production release in two weeks, but I would love to have this merged before then.

[mblayman]

With the added input from @aidanlister, I think we've had enough eyes looking at this to declare victory. Thanks for the contribution, @santiavenda2!