[23.1] Fix ancient bug: incorrect usage of func.coalesce in User model

[jdavcs]

SQLAlchemy BinaryExpression incorrectly assigned as value to user.disk_usage. Should be a numeric value.

This bug was introduced 9 years ago. I believe here's what happened: when this was introduced, there was one other use of func.coalesce related to disk size calculation (here); however, in that other case, the expression was part of a SELECT statement - so it was sent to the database, where it invoked the database's coalesce function, which did what it should do. However, in the new expression, it was not sent to the database. This was never caught because we never checked that value before flushing the session somewhere else, and upon flush, the session did send that value to the database, where that value was evaluated by the db and was stored correctly. However, if we were to access user.disk_usage after calling adjust_disk_usage() but before flushing or committing to the database, we'd get an error, because instead of a decimal, we'd get a SQLAlchemy BinaryExpression type:

(Pdb) u1.total_disk_usage
<sqlalchemy.sql.elements.BinaryExpression object at 0x7f8da9b5c8e0>
(Pdb) str(u1.total_disk_usage)
'coalesce(galaxy_user.disk_usage, :coalesce_1) + :coalesce_2'

This is currently tested in test_galaxy_mapping.py. It works because before accessing this attribute, the test calls session.expunge().

How to test the changes?

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• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[davelopez]

Makes sense, thanks for the detailed explanation.