This bug only appears when using SQLAlchemy with C extensions compiled and a database that does not have a native BOOLEAN type.
If you have a boolean SQLAlchemy column with a MySQL database, when SQLAlchemy sets the value of this column for a particular row, it can be any tinyint value. This function (bolean_to_int) is run to convert the supplied value to an integer for storage: https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/processors.py#L52 When the record is retrieved, and SQLAlchemy is using C extensions, this function is used to convert the stored integer to a boolean value. In this case, the function explicitly throws an error when the value is anything other than None, 0, or 1: https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/cextension/processors.c#L23 I think it's reasonable for a developer using SQLAlchemy to run a web service that takes user input and assigns it to a model's boolean column. If they do not explicitly convert it to a boolean beforehand, assuming that SQLAlchemy will do the necessary conversion, the user may set the boolean column to a value such as "3." Then, any time that record is retrieved SQLAlchemy will throw an error and the request will 500. I think it's a reasonable mistake for the developer to make because the SQLAlchemy docs claim that a constraint is created by default which limits the value stored in the database to 1 or 0: http://docs.sqlalchemy.org/en/latest/core/type_basics.html?highlight=boolean#sqlalchemy.types.Boolean.params.create_constraint It looks like this bug has been seen by others, but the underlying behavior of SQLAlchemy was never addressed: https://groups.google.com/forum/#!searchin/sqlalchemy/boolean/sqlalchemy/n5UadJrTjfA/SBspf9C_WJYJ In my opinion, either the code to retrieve a boolean from an int in the database should be modified to work for any value that SQLAlchemy supports inserting into the column, or the docs should be updated to explain that retrieval will fail in this specific case. It's worth noting that if you do not use C extensions, the code works fine because in Python any non-zero value is implicitly True. - Robert -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
