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POCombining PostgreSQL Enum with a TypeDecorator
 

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    <p>Is there a way to have an Enum class that will both get created automatically when creating a new DB, like the standard Enum, but also connect it to a <code>TypeDecorator</code> that runs <code>process_bind_param</code>?</p> <p>This first code block creates an <code>Enum</code> type that automatically lowercases input before saving it, but, unlike a normal <code>Enum</code>, the specific PostgreSQL enum type isn't created automatically in the database, so running a <code>create_all()</code> causes an error when creating the table, because the <code>language_code</code> type doesn't exist in the PostgreSQL schema. </p> <pre><code>class LowercaseEnum(sqlalchemy.types.TypeDecorator): '''Converts input to lowercase.''' impl = sqlalchemy.types.Enum def process_bind_param(self, value, dialect): return value.lower() class Foo(Model): id = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True) language_code = sqlalchemy.Column(LowercaseEnum(*['de', 'en'], name='language_code')) </code></pre> <p>If, on the other hand, I define my custom type like in this second code block, then it gets created automatically when calling <code>create_all()</code>, but the <code>process_bind_param</code> method is never called when sending values to the database, so the lowercasing doesn't work. </p> <pre><code>class LowercaseEnum(sqlalchemy.dialects.postgresql.ENUM, sqlalchemy.types.TypeDecorator): '''Converts input to lowercase.''' impl = sqlalchemy.types.Enum def process_bind_param(self, value, dialect): return value.lower() </code></pre> <p>I have also tried several different combinations of inheriting from <code>TypeDecorator</code> in a separate class that is mixed-in, and also switching up <code>sqlalchemy.types.Enum</code> and <code>sqlalchemy.dialects.postgresql.ENUM</code>, but it seems no matter what I do, I either get a class that gets created automatically, or a class that runs <code>process_bind_param</code>, but never both.</p>
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