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-rw-r--r--lib/sqlalchemy/sql/compiler.py8
-rw-r--r--lib/sqlalchemy/sql/ddl.py29
2 files changed, 34 insertions, 3 deletions
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index dc3d55039..c56ca1ae4 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -2178,11 +2178,13 @@ class DDLCompiler(Compiled):
for create_column in create.columns:
column = create_column.element
try:
- text += separator
- separator = ", \n"
- text += "\t" + self.process(create_column,
+ processed = self.process(create_column,
first_pk=column.primary_key
and not first_pk)
+ if processed is not None:
+ text += separator
+ separator = ", \n"
+ text += "\t" + processed
if column.primary_key:
first_pk = True
except exc.CompileError as ce:
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.