Eric Lemoine wrote:
>
> Hi
>
> Here's my case: I have
>
> - my own TypeEngine class, MyTypeEngine
> - a Table with a Column using MyTypeEngine:
> table = Table("tablename", metadata,
> Column("columname", MyTypeEngine()),
> autoload=True, autoload_with=engine
> )
> - a class:
> class MyClass(object):
> pass
> - and a mapping:
> mapper(MyClass, table)
>
> Pretty standard. Now, instead of queries like this:
>
> SELECT columnname, ... FROM tablename
>
> I'd like queries like this:
>
> SELECT somefunc(columnname),... FROM tablename
>
> I thought I could get that by overriding my column's ColumnProperty
> with something like that:
>
> mapper(MyClass, table, properties={
> "columname": column_property(
> sql.func.somefunc(table.c.columname).label("columnname")
> )
> })
>
> but it doesn't work as I'd like because it seems that my TypeEngine is
> no longer involved after querying my table - the function returned by
> my TypeEngine's "result_process" method doesn't seem to be called.
>
> Is this expected? Do I have solutions to that problem?
somefunc() needs to specify the return type using type_=MyType, unless its
a known "generic" function that knows to pass through the type of the
first argument as that of the result (such as lower(), for example).
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