#30371: sqlmigrate fails with string defaults on mysql
-------------------------------------+-------------------------------------
     Reporter:  Melvyn Sopacua       |                    Owner:  nobody
         Type:  Bug                  |                   Status:  closed
    Component:  Database layer       |                  Version:  2.1
  (models, ORM)                      |
     Severity:  Release blocker      |               Resolution:  needsinfo
     Keywords:  regression           |             Triage Stage:  Accepted
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------

Comment (by Melvyn Sopacua):

 I think the proper fix here is to confirm both str on value and 'decode'
 attribute on quoted.

 I've tried to add a test for it, but the code never gets called anymore in
 the scope of migrations, because Django no longer transmits default values
 to the backend. So the issue is with [https://github.com/3YOURMIND/django-
 add-default-value our extension] that ensures we can do blue/green
 deployments. Looking at
 [https://github.com/PyMySQL/PyMySQL/blob/master/pymysql/converters.py this
 code] confirms your suspicions that pymysql returns strings.

 Still - when I read the code the first few times until you highlighted the
 fact here, I thought the if clause and the modification are using the same
 value, cause it's such a common pattern you don't read the variable name
 anymore.
 And secondly, it assumes that quoted has the decode() method based on a
 not related test, so I still suggest to fix it like this:


 {{{
 if isinstance(value, str) and callable(getattr(quoted, 'decode', None)):
     quoted = quoted.decode()
 }}}

 This doesn't require the performance hit of force_text and it even
 supports exotic quoted values that implement a decode() method.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/30371#comment:8>
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