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Diffstat (limited to 'lib/sqlalchemy/ext/compiler.py')
| -rw-r--r-- | lib/sqlalchemy/ext/compiler.py | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/sqlalchemy/ext/compiler.py b/lib/sqlalchemy/ext/compiler.py index 56502bd28..7861096f9 100644 --- a/lib/sqlalchemy/ext/compiler.py +++ b/lib/sqlalchemy/ext/compiler.py @@ -131,6 +131,14 @@ A big part of using the compiler extension is subclassing SQLAlchemy expression "column-like" elements. Anything that you'd place in the "columns" clause of a SELECT statement (as well as order by and group by) can derive from this - the object will automatically have Python "comparison" behavior. + + :class:`~sqlalchemy.sql.expression.ColumnElement` classes want to have a + ``type`` member which is expression's return type. This can be established + at the instance level in the constructor, or at the class level if its + generally constant:: + + class timestamp(ColumnElement): + type = TIMESTAMP() * :class:`~sqlalchemy.sql.expression.FunctionElement` - This is a hybrid of a ``ColumnElement`` and a "from clause" like object, and represents a SQL |