#32793: Problem with decimal field when upgrade version
-------------------------------------+-------------------------------------
     Reporter:  Mohsen Tamiz         |                    Owner:  nobody
         Type:  Bug                  |                   Status:  new
    Component:  Database layer       |                  Version:  3.2
  (models, ORM)                      |
     Severity:  Release blocker      |               Resolution:
     Keywords:  decimal              |             Triage Stage:  Accepted
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):

 * severity:  Normal => Release blocker
 * stage:  Unreviewed => Accepted


Comment:

 I've not looked into how but we should fix this.

 I believe it happens to be addressed in MySQL 8.0.21 (relased 2020-07-13)
 due to implicit casts injections as is likely why it wasn't caught by our
 test suite

 https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-21.html

 > Building on work done in MySQL 8.0.18, the server now performs injection
 of casts into queries to avoid mismatches when comparing string data types
 with those of numeric or temporal types; as when comparing numeric and
 temporal types, the optimizer now adds casting operations in the item tree
 inside expressions and conditions in which the data type of the argument
 and the expected data type do not match. This makes queries in which
 string types are compared with numeric or temporal types equivalent to
 queries which are compliant with the SQL standard, while maintaining
 backwards compatibility with previous releases of MySQL.

 It's not clear to me whether this was broken in 8.0.18 and then resolved
 in 8.0.21

 https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-18.html

 > MySQL now performs injection of casts into queries to avoid certain data
 type mismatches; that is, the optimizer now adds casting operations in the
 item tree inside expressions and conditions in which the data type of the
 argument and the expected data type do not match. This makes the query as
 executed equivalent to one which is compliant with the SQL standard while
 maintaining backwards compatibility with previous releases of MySQL.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/32793#comment:2>
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