Fix select for update

[dag18e]

Fixes #866

Description of the Change

Oracle Database 12c does not allow limits on select_for_update statements. This change removes the limit and instead just uses a get.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[coveralls]

Pull Request Test Coverage Report for Build 1522

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.06%) to 94.954%

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Files with Coverage Reduction	New Missed Lines	%
oauth2_provider/models.py	1	97.0%

Totals
Change from base Build 1520:	-0.06%
Covered Lines:	1336
Relevant Lines:	1407

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💛 - Coveralls

[MattBlack85]

@dag18e I understand your point but your change is gonna drop the lock on the database row and it's completely changing the intended behaviour

[MattBlack85]

@dag18e 🤦 I was reviewing this on my mobile and I didn't notice how it really was. Ignore my first comment.
I have another question tho, I suppose .filter() was used cause we may have more than one token, if we use .get() and there is more than one token the exception is not caught?
Maybe a simple slicing could be used instead?

Also, an entry into the CHANGELOG is required

[dag18e]

@MattBlack85 Hey man, sorry about the delay here. Had some other stuff come up + holidays so I'm just getting back to this. On your note about filter vs get, I changed it a bit to use filter. Basically, I wrap it in a list and grab the first in the list.

This ought to retain the original functionality, but it also doesn't apply a limit to the request so it works with Oracle 12c.

I'll be adding info to docs and changelog once tests pass Travis.

[codecov]

Codecov Report

Merging #906 (fde3b61) into master (3010059) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #906   +/-   ##
=======================================
  Coverage   95.04%   95.04%           
=======================================
  Files          25       25           
  Lines        1070     1070           
=======================================
  Hits         1017     1017           
  Misses         53       53           

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[dag18e]

@MattBlack85 Actually, do you think I need to add anything to the documentation? I don't really feel this change is worthy of a change there, but you'd know better than me.

[n2ygk]

@MattBlack85 I think this is good with the change to using a transaction.

Thanks @dag18e

[MattBlack85]

@dag18e @n2ygk I think we added some things here that are not really needed:

1. AFAIK .filter() can't raise DoesNotExist
2. L412 casts the Queryset to a list and then slicing, I do no think this is needed and this slows down things a bit

I feel these things should be addressed in a follow up PR