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Diffstat (limited to 'lib/sqlalchemy/sql/ddl.py')
-rw-r--r-- | lib/sqlalchemy/sql/ddl.py | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/ddl.py b/lib/sqlalchemy/sql/ddl.py index 8159ca472..a0163ad7a 100644 --- a/lib/sqlalchemy/sql/ddl.py +++ b/lib/sqlalchemy/sql/ddl.py @@ -548,6 +548,35 @@ class CreateColumn(_DDLCompiles): PRIMARY KEY (x) ) + The :class:`.CreateColumn` construct can also be used to skip certain + columns when producing a ``CREATE TABLE``. This is accomplished by + creating a compilation rule that conditionally returns ``None``. + For example, to produce a + :class:`.Table` which includes the Postgresql system column ``xmin``, + but omits this column from the ``CREATE TABLE``:: + + from sqlalchemy.schema import CreateColumn + + @compiles(CreateColumn) + def skip_xmin(element, compiler, **kw): + if element.element.name == 'xmin': + return None + else: + return compiler.visit_create_column(element, **kw) + + + my_table = Table('mytable', metadata, + Column('id', Integer, primary_key=True), + Column('xmin', Integer) + ) + + Above, a :class:`.CreateTable` construct will generate a ``CREATE TABLE`` + which only includes the ``id`` column in the string; the ``xmin`` column + will be omitted. + + .. versionadded:: 0.8.3 The :class:`.CreateColumn` construct supports + skipping of columns by returning ``None`` from a custom compilation rule. + .. versionadded:: 0.8 The :class:`.CreateColumn` construct was added to support custom column creation styles. |