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calibre-web/lib/sqlalchemy/schema.py

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# sqlalchemy/schema.py
# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""The schema module provides the building blocks for database metadata.
Each element within this module describes a database entity which can be
created and dropped, or is otherwise part of such an entity. Examples include
tables, columns, sequences, and indexes.
All entities are subclasses of :class:`~sqlalchemy.schema.SchemaItem`, and as
defined in this module they are intended to be agnostic of any vendor-specific
constructs.
A collection of entities are grouped into a unit called
:class:`~sqlalchemy.schema.MetaData`. MetaData serves as a logical grouping of
schema elements, and can also be associated with an actual database connection
such that operations involving the contained elements can contact the database
as needed.
Two of the elements here also build upon their "syntactic" counterparts, which
are defined in :class:`~sqlalchemy.sql.expression.`, specifically
:class:`~sqlalchemy.schema.Table` and :class:`~sqlalchemy.schema.Column`.
Since these objects are part of the SQL expression language, they are usable
as components in SQL expressions.
"""
from __future__ import with_statement
import re
import inspect
from . import exc, util, dialects, event, events, inspection
from .sql import expression, visitors
ddl = util.importlater("sqlalchemy.engine", "ddl")
sqlutil = util.importlater("sqlalchemy.sql", "util")
url = util.importlater("sqlalchemy.engine", "url")
sqltypes = util.importlater("sqlalchemy", "types")
__all__ = ['SchemaItem', 'Table', 'Column', 'ForeignKey', 'Sequence', 'Index',
'ForeignKeyConstraint', 'PrimaryKeyConstraint', 'CheckConstraint',
'UniqueConstraint', 'DefaultGenerator', 'Constraint', 'MetaData',
'ThreadLocalMetaData', 'SchemaVisitor', 'PassiveDefault',
'DefaultClause', 'FetchedValue', 'ColumnDefault', 'DDL',
'CreateTable', 'DropTable', 'CreateSequence', 'DropSequence',
'AddConstraint', 'DropConstraint',
]
__all__.sort()
RETAIN_SCHEMA = util.symbol('retain_schema')
class SchemaItem(events.SchemaEventTarget, visitors.Visitable):
"""Base class for items that define a database schema."""
__visit_name__ = 'schema_item'
quote = None
def _init_items(self, *args):
"""Initialize the list of child items for this SchemaItem."""
for item in args:
if item is not None:
item._set_parent_with_dispatch(self)
def get_children(self, **kwargs):
"""used to allow SchemaVisitor access"""
return []
def __repr__(self):
return util.generic_repr(self)
@util.memoized_property
def info(self):
"""Info dictionary associated with the object, allowing user-defined
data to be associated with this :class:`.SchemaItem`.
The dictionary is automatically generated when first accessed.
It can also be specified in the constructor of some objects,
such as :class:`.Table` and :class:`.Column`.
"""
return {}
def _get_table_key(name, schema):
if schema is None:
return name
else:
return schema + "." + name
def _validate_dialect_kwargs(kwargs, name):
# validate remaining kwargs that they all specify DB prefixes
for k in kwargs:
m = re.match('^(.+?)_.*', k)
if m is None:
raise TypeError("Additional arguments should be "
"named <dialectname>_<argument>, got '%s'" % k)
inspection._self_inspects(SchemaItem)
class Table(SchemaItem, expression.TableClause):
"""Represent a table in a database.
e.g.::
mytable = Table("mytable", metadata,
Column('mytable_id', Integer, primary_key=True),
Column('value', String(50))
)
The :class:`.Table` object constructs a unique instance of itself based
on its name and optional schema name within the given
:class:`.MetaData` object. Calling the :class:`.Table`
constructor with the same name and same :class:`.MetaData` argument
a second time will return the *same* :class:`.Table` object - in this way
the :class:`.Table` constructor acts as a registry function.
.. seealso::
:ref:`metadata_describing` - Introduction to database metadata
Constructor arguments are as follows:
:param name: The name of this table as represented in the database.
This property, along with the *schema*, indicates the *singleton
identity* of this table in relation to its parent :class:`.MetaData`.
Additional calls to :class:`.Table` with the same name, metadata,
and schema name will return the same :class:`.Table` object.
Names which contain no upper case characters
will be treated as case insensitive names, and will not be quoted
unless they are a reserved word. Names with any number of upper
case characters will be quoted and sent exactly. Note that this
behavior applies even for databases which standardize upper
case names as case insensitive such as Oracle.
:param metadata: a :class:`.MetaData` object which will contain this
table. The metadata is used as a point of association of this table
with other tables which are referenced via foreign key. It also
may be used to associate this table with a particular
:class:`.Connectable`.
:param \*args: Additional positional arguments are used primarily
to add the list of :class:`.Column` objects contained within this
table. Similar to the style of a CREATE TABLE statement, other
:class:`.SchemaItem` constructs may be added here, including
:class:`.PrimaryKeyConstraint`, and :class:`.ForeignKeyConstraint`.
:param autoload: Defaults to False: the Columns for this table should
be reflected from the database. Usually there will be no Column
objects in the constructor if this property is set.
:param autoload_replace: If ``True``, when using ``autoload=True``
and ``extend_existing=True``,
replace ``Column`` objects already present in the ``Table`` that's
in the ``MetaData`` registry with
what's reflected. Otherwise, all existing columns will be
excluded from the reflection process. Note that this does
not impact ``Column`` objects specified in the same call to ``Table``
which includes ``autoload``, those always take precedence.
Defaults to ``True``.
.. versionadded:: 0.7.5
:param autoload_with: If autoload==True, this is an optional Engine
or Connection instance to be used for the table reflection. If
``None``, the underlying MetaData's bound connectable will be used.
:param extend_existing: When ``True``, indicates that if this
:class:`.Table` is already present in the given :class:`.MetaData`,
apply further arguments within the constructor to the existing
:class:`.Table`.
If ``extend_existing`` or ``keep_existing`` are not set, an error is
raised if additional table modifiers are specified when
the given :class:`.Table` is already present in the :class:`.MetaData`.
.. versionchanged:: 0.7.4
``extend_existing`` will work in conjunction
with ``autoload=True`` to run a new reflection operation against
the database; new :class:`.Column` objects will be produced
from database metadata to replace those existing with the same
name, and additional :class:`.Column` objects not present
in the :class:`.Table` will be added.
As is always the case with ``autoload=True``, :class:`.Column`
objects can be specified in the same :class:`.Table` constructor,
which will take precedence. I.e.::
Table("mytable", metadata,
Column('y', Integer),
extend_existing=True,
autoload=True,
autoload_with=engine
)
The above will overwrite all columns within ``mytable`` which
are present in the database, except for ``y`` which will be used as is
from the above definition. If the ``autoload_replace`` flag
is set to False, no existing columns will be replaced.
:param implicit_returning: True by default - indicates that
RETURNING can be used by default to fetch newly inserted primary key
values, for backends which support this. Note that
create_engine() also provides an implicit_returning flag.
:param include_columns: A list of strings indicating a subset of
columns to be loaded via the ``autoload`` operation; table columns who
aren't present in this list will not be represented on the resulting
``Table`` object. Defaults to ``None`` which indicates all columns
should be reflected.
:param info: Optional data dictionary which will be populated into the
:attr:`.SchemaItem.info` attribute of this object.
:param keep_existing: When ``True``, indicates that if this Table
is already present in the given :class:`.MetaData`, ignore
further arguments within the constructor to the existing
:class:`.Table`, and return the :class:`.Table` object as
originally created. This is to allow a function that wishes
to define a new :class:`.Table` on first call, but on
subsequent calls will return the same :class:`.Table`,
without any of the declarations (particularly constraints)
being applied a second time. Also see extend_existing.
If extend_existing or keep_existing are not set, an error is
raised if additional table modifiers are specified when
the given :class:`.Table` is already present in the :class:`.MetaData`.
:param listeners: A list of tuples of the form ``(<eventname>, <fn>)``
which will be passed to :func:`.event.listen` upon construction.
This alternate hook to :func:`.event.listen` allows the establishment
of a listener function specific to this :class:`.Table` before
the "autoload" process begins. Particularly useful for
the :meth:`.DDLEvents.column_reflect` event::
def listen_for_reflect(table, column_info):
"handle the column reflection event"
# ...
t = Table(
'sometable',
autoload=True,
listeners=[
('column_reflect', listen_for_reflect)
])
:param mustexist: When ``True``, indicates that this Table must already
be present in the given :class:`.MetaData` collection, else
an exception is raised.
:param prefixes:
A list of strings to insert after CREATE in the CREATE TABLE
statement. They will be separated by spaces.
:param quote: Force quoting of this table's name on or off, corresponding
to ``True`` or ``False``. When left at its default of ``None``,
the column identifier will be quoted according to whether the name is
case sensitive (identifiers with at least one upper case character are
treated as case sensitive), or if it's a reserved word. This flag
is only needed to force quoting of a reserved word which is not known
by the SQLAlchemy dialect.
:param quote_schema: same as 'quote' but applies to the schema identifier.
:param schema: The *schema name* for this table, which is required if
the table resides in a schema other than the default selected schema
for the engine's database connection. Defaults to ``None``.
:param useexisting: Deprecated. Use extend_existing.
"""
__visit_name__ = 'table'
def __new__(cls, *args, **kw):
if not args:
# python3k pickle seems to call this
return object.__new__(cls)
try:
name, metadata, args = args[0], args[1], args[2:]
except IndexError:
raise TypeError("Table() takes at least two arguments")
schema = kw.get('schema', None)
if schema is None:
schema = metadata.schema
keep_existing = kw.pop('keep_existing', False)
extend_existing = kw.pop('extend_existing', False)
if 'useexisting' in kw:
msg = "useexisting is deprecated. Use extend_existing."
util.warn_deprecated(msg)
if extend_existing:
msg = "useexisting is synonymous with extend_existing."
raise exc.ArgumentError(msg)
extend_existing = kw.pop('useexisting', False)
if keep_existing and extend_existing:
msg = "keep_existing and extend_existing are mutually exclusive."
raise exc.ArgumentError(msg)
mustexist = kw.pop('mustexist', False)
key = _get_table_key(name, schema)
if key in metadata.tables:
if not keep_existing and not extend_existing and bool(args):
raise exc.InvalidRequestError(
"Table '%s' is already defined for this MetaData "
"instance. Specify 'extend_existing=True' "
"to redefine "
"options and columns on an "
"existing Table object." % key)
table = metadata.tables[key]
if extend_existing:
table._init_existing(*args, **kw)
return table
else:
if mustexist:
raise exc.InvalidRequestError(
"Table '%s' not defined" % (key))
table = object.__new__(cls)
table.dispatch.before_parent_attach(table, metadata)
metadata._add_table(name, schema, table)
try:
table._init(name, metadata, *args, **kw)
table.dispatch.after_parent_attach(table, metadata)
return table
except:
metadata._remove_table(name, schema)
raise
def __init__(self, *args, **kw):
"""Constructor for :class:`~.schema.Table`.
This method is a no-op. See the top-level
documentation for :class:`~.schema.Table`
for constructor arguments.
"""
# __init__ is overridden to prevent __new__ from
# calling the superclass constructor.
def _init(self, name, metadata, *args, **kwargs):
super(Table, self).__init__(name)
self.metadata = metadata
self.schema = kwargs.pop('schema', None)
if self.schema is None:
self.schema = metadata.schema
self.quote_schema = kwargs.pop(
'quote_schema', metadata.quote_schema)
else:
self.quote_schema = kwargs.pop('quote_schema', None)
self.indexes = set()
self.constraints = set()
self._columns = expression.ColumnCollection()
PrimaryKeyConstraint()._set_parent_with_dispatch(self)
self.foreign_keys = set()
self._extra_dependencies = set()
self.kwargs = {}
if self.schema is not None:
self.fullname = "%s.%s" % (self.schema, self.name)
else:
self.fullname = self.name
autoload = kwargs.pop('autoload', False)
autoload_with = kwargs.pop('autoload_with', None)
# this argument is only used with _init_existing()
kwargs.pop('autoload_replace', True)
include_columns = kwargs.pop('include_columns', None)
self.implicit_returning = kwargs.pop('implicit_returning', True)
self.quote = kwargs.pop('quote', None)
if 'info' in kwargs:
self.info = kwargs.pop('info')
if 'listeners' in kwargs:
listeners = kwargs.pop('listeners')
for evt, fn in listeners:
event.listen(self, evt, fn)
self._prefixes = kwargs.pop('prefixes', [])
self._extra_kwargs(**kwargs)
# load column definitions from the database if 'autoload' is defined
# we do it after the table is in the singleton dictionary to support
# circular foreign keys
if autoload:
self._autoload(metadata, autoload_with, include_columns)
# initialize all the column, etc. objects. done after reflection to
# allow user-overrides
self._init_items(*args)
def _autoload(self, metadata, autoload_with, include_columns,
exclude_columns=()):
if self.primary_key.columns:
PrimaryKeyConstraint(*[
c for c in self.primary_key.columns
if c.key in exclude_columns
])._set_parent_with_dispatch(self)
if autoload_with:
autoload_with.run_callable(
autoload_with.dialect.reflecttable,
self, include_columns, exclude_columns
)
else:
bind = _bind_or_error(metadata,
msg="No engine is bound to this Table's MetaData. "
"Pass an engine to the Table via "
"autoload_with=<someengine>, "
"or associate the MetaData with an engine via "
"metadata.bind=<someengine>")
bind.run_callable(
bind.dialect.reflecttable,
self, include_columns, exclude_columns
)
@property
def _sorted_constraints(self):
"""Return the set of constraints as a list, sorted by creation
order.
"""
return sorted(self.constraints, key=lambda c: c._creation_order)
def _init_existing(self, *args, **kwargs):
autoload = kwargs.pop('autoload', False)
autoload_with = kwargs.pop('autoload_with', None)
autoload_replace = kwargs.pop('autoload_replace', True)
schema = kwargs.pop('schema', None)
if schema and schema != self.schema:
raise exc.ArgumentError(
"Can't change schema of existing table from '%s' to '%s'",
(self.schema, schema))
include_columns = kwargs.pop('include_columns', None)
if include_columns is not None:
for c in self.c:
if c.name not in include_columns:
self._columns.remove(c)
for key in ('quote', 'quote_schema'):
if key in kwargs:
setattr(self, key, kwargs.pop(key))
if 'info' in kwargs:
self.info = kwargs.pop('info')
if autoload:
if not autoload_replace:
exclude_columns = [c.name for c in self.c]
else:
exclude_columns = ()
self._autoload(
self.metadata, autoload_with, include_columns, exclude_columns)
self._extra_kwargs(**kwargs)
self._init_items(*args)
def _extra_kwargs(self, **kwargs):
# validate remaining kwargs that they all specify DB prefixes
_validate_dialect_kwargs(kwargs, "Table")
self.kwargs.update(kwargs)
def _init_collections(self):
pass
@util.memoized_property
def _autoincrement_column(self):
for col in self.primary_key:
if col.autoincrement and \
col.type._type_affinity is not None and \
issubclass(col.type._type_affinity, sqltypes.Integer) and \
(not col.foreign_keys or col.autoincrement == 'ignore_fk') and \
isinstance(col.default, (type(None), Sequence)) and \
(col.server_default is None or col.server_default.reflected):
return col
@property
def key(self):
return _get_table_key(self.name, self.schema)
def __repr__(self):
return "Table(%s)" % ', '.join(
[repr(self.name)] + [repr(self.metadata)] +
[repr(x) for x in self.columns] +
["%s=%s" % (k, repr(getattr(self, k))) for k in ['schema']])
def __str__(self):
return _get_table_key(self.description, self.schema)
@property
def bind(self):
"""Return the connectable associated with this Table."""
return self.metadata and self.metadata.bind or None
def add_is_dependent_on(self, table):
"""Add a 'dependency' for this Table.
This is another Table object which must be created
first before this one can, or dropped after this one.
Usually, dependencies between tables are determined via
ForeignKey objects. However, for other situations that
create dependencies outside of foreign keys (rules, inheriting),
this method can manually establish such a link.
"""
self._extra_dependencies.add(table)
def append_column(self, column):
"""Append a :class:`~.schema.Column` to this :class:`~.schema.Table`.
The "key" of the newly added :class:`~.schema.Column`, i.e. the
value of its ``.key`` attribute, will then be available
in the ``.c`` collection of this :class:`~.schema.Table`, and the
column definition will be included in any CREATE TABLE, SELECT,
UPDATE, etc. statements generated from this :class:`~.schema.Table`
construct.
Note that this does **not** change the definition of the table
as it exists within any underlying database, assuming that
table has already been created in the database. Relational
databases support the addition of columns to existing tables
using the SQL ALTER command, which would need to be
emitted for an already-existing table that doesn't contain
the newly added column.
"""
column._set_parent_with_dispatch(self)
def append_constraint(self, constraint):
"""Append a :class:`~.schema.Constraint` to this
:class:`~.schema.Table`.
This has the effect of the constraint being included in any
future CREATE TABLE statement, assuming specific DDL creation
events have not been associated with the given
:class:`~.schema.Constraint` object.
Note that this does **not** produce the constraint within the
relational database automatically, for a table that already exists
in the database. To add a constraint to an
existing relational database table, the SQL ALTER command must
be used. SQLAlchemy also provides the
:class:`.AddConstraint` construct which can produce this SQL when
invoked as an executable clause.
"""
constraint._set_parent_with_dispatch(self)
def append_ddl_listener(self, event_name, listener):
"""Append a DDL event listener to this ``Table``.
Deprecated. See :class:`.DDLEvents`.
"""
def adapt_listener(target, connection, **kw):
listener(event_name, target, connection)
event.listen(self, "" + event_name.replace('-', '_'), adapt_listener)
def _set_parent(self, metadata):
metadata._add_table(self.name, self.schema, self)
self.metadata = metadata
def get_children(self, column_collections=True,
schema_visitor=False, **kw):
if not schema_visitor:
return expression.TableClause.get_children(
self, column_collections=column_collections, **kw)
else:
if column_collections:
return list(self.columns)
else:
return []
def exists(self, bind=None):
"""Return True if this table exists."""
if bind is None:
bind = _bind_or_error(self)
return bind.run_callable(bind.dialect.has_table,
self.name, schema=self.schema)
def create(self, bind=None, checkfirst=False):
"""Issue a ``CREATE`` statement for this
:class:`.Table`, using the given :class:`.Connectable`
for connectivity.
.. seealso::
:meth:`.MetaData.create_all`.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaGenerator,
self,
checkfirst=checkfirst)
def drop(self, bind=None, checkfirst=False):
"""Issue a ``DROP`` statement for this
:class:`.Table`, using the given :class:`.Connectable`
for connectivity.
.. seealso::
:meth:`.MetaData.drop_all`.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaDropper,
self,
checkfirst=checkfirst)
def tometadata(self, metadata, schema=RETAIN_SCHEMA):
"""Return a copy of this :class:`.Table` associated with a different
:class:`.MetaData`.
E.g.::
some_engine = create_engine("sqlite:///some.db")
# create two metadata
meta1 = MetaData()
meta2 = MetaData()
# load 'users' from the sqlite engine
users_table = Table('users', meta1, autoload=True,
autoload_with=some_engine)
# create the same Table object for the plain metadata
users_table_2 = users_table.tometadata(meta2)
:param metadata: Target :class:`.MetaData` object.
:param schema: Optional string name of a target schema, or
``None`` for no schema. The :class:`.Table` object will be
given this schema name upon copy. Defaults to the special
symbol :attr:`.RETAIN_SCHEMA` which indicates no change should be
made to the schema name of the resulting :class:`.Table`.
"""
if schema is RETAIN_SCHEMA:
schema = self.schema
elif schema is None:
schema = metadata.schema
key = _get_table_key(self.name, schema)
if key in metadata.tables:
util.warn("Table '%s' already exists within the given "
"MetaData - not copying." % self.description)
return metadata.tables[key]
args = []
for c in self.columns:
args.append(c.copy(schema=schema))
table = Table(
self.name, metadata, schema=schema,
*args, **self.kwargs
)
for c in self.constraints:
table.append_constraint(c.copy(schema=schema, target_table=table))
for index in self.indexes:
# skip indexes that would be generated
# by the 'index' flag on Column
if len(index.columns) == 1 and \
list(index.columns)[0].index:
continue
Index(index.name,
unique=index.unique,
*[table.c[col] for col in index.columns.keys()],
**index.kwargs)
table.dispatch._update(self.dispatch)
return table
class Column(SchemaItem, expression.ColumnClause):
"""Represents a column in a database table."""
__visit_name__ = 'column'
def __init__(self, *args, **kwargs):
"""
Construct a new ``Column`` object.
:param name: The name of this column as represented in the database.
This argument may be the first positional argument, or specified
via keyword.
Names which contain no upper case characters
will be treated as case insensitive names, and will not be quoted
unless they are a reserved word. Names with any number of upper
case characters will be quoted and sent exactly. Note that this
behavior applies even for databases which standardize upper
case names as case insensitive such as Oracle.
The name field may be omitted at construction time and applied
later, at any time before the Column is associated with a
:class:`.Table`. This is to support convenient
usage within the :mod:`~sqlalchemy.ext.declarative` extension.
:param type\_: The column's type, indicated using an instance which
subclasses :class:`~sqlalchemy.types.TypeEngine`. If no arguments
are required for the type, the class of the type can be sent
as well, e.g.::
# use a type with arguments
Column('data', String(50))
# use no arguments
Column('level', Integer)
The ``type`` argument may be the second positional argument
or specified by keyword.
There is partial support for automatic detection of the
type based on that of a :class:`.ForeignKey` associated
with this column, if the type is specified as ``None``.
However, this feature is not fully implemented and
may not function in all cases.
:param \*args: Additional positional arguments include various
:class:`.SchemaItem` derived constructs which will be applied
as options to the column. These include instances of
:class:`.Constraint`, :class:`.ForeignKey`, :class:`.ColumnDefault`,
and :class:`.Sequence`. In some cases an equivalent keyword
argument is available such as ``server_default``, ``default``
and ``unique``.
:param autoincrement: This flag may be set to ``False`` to
indicate an integer primary key column that should not be
considered to be the "autoincrement" column, that is
the integer primary key column which generates values
implicitly upon INSERT and whose value is usually returned
via the DBAPI cursor.lastrowid attribute. It defaults
to ``True`` to satisfy the common use case of a table
with a single integer primary key column. If the table
has a composite primary key consisting of more than one
integer column, set this flag to True only on the
column that should be considered "autoincrement".
The setting *only* has an effect for columns which are:
* Integer derived (i.e. INT, SMALLINT, BIGINT).
* Part of the primary key
* Are not referenced by any foreign keys, unless
the value is specified as ``'ignore_fk'``
.. versionadded:: 0.7.4
* have no server side or client side defaults (with the exception
of Postgresql SERIAL).
The setting has these two effects on columns that meet the
above criteria:
* DDL issued for the column will include database-specific
keywords intended to signify this column as an
"autoincrement" column, such as AUTO INCREMENT on MySQL,
SERIAL on Postgresql, and IDENTITY on MS-SQL. It does
*not* issue AUTOINCREMENT for SQLite since this is a
special SQLite flag that is not required for autoincrementing
behavior. See the SQLite dialect documentation for
information on SQLite's AUTOINCREMENT.
* The column will be considered to be available as
cursor.lastrowid or equivalent, for those dialects which
"post fetch" newly inserted identifiers after a row has
been inserted (SQLite, MySQL, MS-SQL). It does not have
any effect in this regard for databases that use sequences
to generate primary key identifiers (i.e. Firebird, Postgresql,
Oracle).
.. versionchanged:: 0.7.4
``autoincrement`` accepts a special value ``'ignore_fk'``
to indicate that autoincrementing status regardless of foreign
key references. This applies to certain composite foreign key
setups, such as the one demonstrated in the ORM documentation
at :ref:`post_update`.
:param default: A scalar, Python callable, or
:class:`.ColumnElement` expression representing the
*default value* for this column, which will be invoked upon insert
if this column is otherwise not specified in the VALUES clause of
the insert. This is a shortcut to using :class:`.ColumnDefault` as
a positional argument; see that class for full detail on the
structure of the argument.
Contrast this argument to ``server_default`` which creates a
default generator on the database side.
:param doc: optional String that can be used by the ORM or similar
to document attributes. This attribute does not render SQL
comments (a future attribute 'comment' will achieve that).
:param key: An optional string identifier which will identify this
``Column`` object on the :class:`.Table`. When a key is provided,
this is the only identifier referencing the ``Column`` within the
application, including ORM attribute mapping; the ``name`` field
is used only when rendering SQL.
:param index: When ``True``, indicates that the column is indexed.
This is a shortcut for using a :class:`.Index` construct on the
table. To specify indexes with explicit names or indexes that
contain multiple columns, use the :class:`.Index` construct
instead.
:param info: Optional data dictionary which will be populated into the
:attr:`.SchemaItem.info` attribute of this object.
:param nullable: If set to the default of ``True``, indicates the
column will be rendered as allowing NULL, else it's rendered as
NOT NULL. This parameter is only used when issuing CREATE TABLE
statements.
:param onupdate: A scalar, Python callable, or
:class:`~sqlalchemy.sql.expression.ClauseElement` representing a
default value to be applied to the column within UPDATE
statements, which wil be invoked upon update if this column is not
present in the SET clause of the update. This is a shortcut to
using :class:`.ColumnDefault` as a positional argument with
``for_update=True``.
:param primary_key: If ``True``, marks this column as a primary key
column. Multiple columns can have this flag set to specify
composite primary keys. As an alternative, the primary key of a
:class:`.Table` can be specified via an explicit
:class:`.PrimaryKeyConstraint` object.
:param server_default: A :class:`.FetchedValue` instance, str, Unicode
or :func:`~sqlalchemy.sql.expression.text` construct representing
the DDL DEFAULT value for the column.
String types will be emitted as-is, surrounded by single quotes::
Column('x', Text, server_default="val")
x TEXT DEFAULT 'val'
A :func:`~sqlalchemy.sql.expression.text` expression will be
rendered as-is, without quotes::
Column('y', DateTime, server_default=text('NOW()'))0
y DATETIME DEFAULT NOW()
Strings and text() will be converted into a :class:`.DefaultClause`
object upon initialization.
Use :class:`.FetchedValue` to indicate that an already-existing
column will generate a default value on the database side which
will be available to SQLAlchemy for post-fetch after inserts. This
construct does not specify any DDL and the implementation is left
to the database, such as via a trigger.
:param server_onupdate: A :class:`.FetchedValue` instance
representing a database-side default generation function. This
indicates to SQLAlchemy that a newly generated value will be
available after updates. This construct does not specify any DDL
and the implementation is left to the database, such as via a
trigger.
:param quote: Force quoting of this column's name on or off,
corresponding to ``True`` or ``False``. When left at its default
of ``None``, the column identifier will be quoted according to
whether the name is case sensitive (identifiers with at least one
upper case character are treated as case sensitive), or if it's a
reserved word. This flag is only needed to force quoting of a
reserved word which is not known by the SQLAlchemy dialect.
:param unique: When ``True``, indicates that this column contains a
unique constraint, or if ``index`` is ``True`` as well, indicates
that the :class:`.Index` should be created with the unique flag.
To specify multiple columns in the constraint/index or to specify
an explicit name, use the :class:`.UniqueConstraint` or
:class:`.Index` constructs explicitly.
:param system: When ``True``, indicates this is a "system" column,
that is a column which is automatically made available by the
database, and should not be included in the columns list for a
``CREATE TABLE`` statement.
For more elaborate scenarios where columns should be conditionally
rendered differently on different backends, consider custom
compilation rules for :class:`.CreateColumn`.
..versionadded:: 0.8.3 Added the ``system=True`` parameter to
:class:`.Column`.
"""
name = kwargs.pop('name', None)
type_ = kwargs.pop('type_', None)
args = list(args)
if args:
if isinstance(args[0], basestring):
if name is not None:
raise exc.ArgumentError(
"May not pass name positionally and as a keyword.")
name = args.pop(0)
if args:
coltype = args[0]
if (isinstance(coltype, sqltypes.TypeEngine) or
(isinstance(coltype, type) and
issubclass(coltype, sqltypes.TypeEngine))):
if type_ is not None:
raise exc.ArgumentError(
"May not pass type_ positionally and as a keyword.")
type_ = args.pop(0)
no_type = type_ is None
super(Column, self).__init__(name, None, type_)
self.key = kwargs.pop('key', name)
self.primary_key = kwargs.pop('primary_key', False)
self.nullable = kwargs.pop('nullable', not self.primary_key)
self.default = kwargs.pop('default', None)
self.server_default = kwargs.pop('server_default', None)
self.server_onupdate = kwargs.pop('server_onupdate', None)
# these default to None because .index and .unique is *not*
# an informational flag about Column - there can still be an
# Index or UniqueConstraint referring to this Column.
self.index = kwargs.pop('index', None)
self.unique = kwargs.pop('unique', None)
self.system = kwargs.pop('system', False)
self.quote = kwargs.pop('quote', None)
self.doc = kwargs.pop('doc', None)
self.onupdate = kwargs.pop('onupdate', None)
self.autoincrement = kwargs.pop('autoincrement', True)
self.constraints = set()
self.foreign_keys = set()
# check if this Column is proxying another column
if '_proxies' in kwargs:
self._proxies = kwargs.pop('_proxies')
# otherwise, add DDL-related events
elif isinstance(self.type, sqltypes.SchemaType):
self.type._set_parent_with_dispatch(self)
if self.default is not None:
if isinstance(self.default, (ColumnDefault, Sequence)):
args.append(self.default)
else:
if getattr(self.type, '_warn_on_bytestring', False):
# Py3K
#if isinstance(self.default, bytes):
# Py2K
if isinstance(self.default, str):
# end Py2K
util.warn("Unicode column received non-unicode "
"default value.")
args.append(ColumnDefault(self.default))
if self.server_default is not None:
if isinstance(self.server_default, FetchedValue):
args.append(self.server_default._as_for_update(False))
else:
args.append(DefaultClause(self.server_default))
if self.onupdate is not None:
if isinstance(self.onupdate, (ColumnDefault, Sequence)):
args.append(self.onupdate)
else:
args.append(ColumnDefault(self.onupdate, for_update=True))
if self.server_onupdate is not None:
if isinstance(self.server_onupdate, FetchedValue):
args.append(self.server_onupdate._as_for_update(True))
else:
args.append(DefaultClause(self.server_onupdate,
for_update=True))
self._init_items(*args)
if not self.foreign_keys and no_type:
raise exc.ArgumentError("'type' is required on Column objects "
"which have no foreign keys.")
util.set_creation_order(self)
if 'info' in kwargs:
self.info = kwargs.pop('info')
if kwargs:
raise exc.ArgumentError(
"Unknown arguments passed to Column: " + repr(kwargs.keys()))
def __str__(self):
if self.name is None:
return "(no name)"
elif self.table is not None:
if self.table.named_with_column:
return (self.table.description + "." + self.description)
else:
return self.description
else:
return self.description
def references(self, column):
"""Return True if this Column references the given column via foreign
key."""
for fk in self.foreign_keys:
if fk.column.proxy_set.intersection(column.proxy_set):
return True
else:
return False
def append_foreign_key(self, fk):
fk._set_parent_with_dispatch(self)
def __repr__(self):
kwarg = []
if self.key != self.name:
kwarg.append('key')
if self.primary_key:
kwarg.append('primary_key')
if not self.nullable:
kwarg.append('nullable')
if self.onupdate:
kwarg.append('onupdate')
if self.default:
kwarg.append('default')
if self.server_default:
kwarg.append('server_default')
return "Column(%s)" % ', '.join(
[repr(self.name)] + [repr(self.type)] +
[repr(x) for x in self.foreign_keys if x is not None] +
[repr(x) for x in self.constraints] +
[(self.table is not None and "table=<%s>" %
self.table.description or "table=None")] +
["%s=%s" % (k, repr(getattr(self, k))) for k in kwarg])
def _set_parent(self, table):
if not self.name:
raise exc.ArgumentError(
"Column must be constructed with a non-blank name or "
"assign a non-blank .name before adding to a Table.")
if self.key is None:
self.key = self.name
existing = getattr(self, 'table', None)
if existing is not None and existing is not table:
raise exc.ArgumentError(
"Column object already assigned to Table '%s'" %
existing.description)
if self.key in table._columns:
col = table._columns.get(self.key)
if col is not self:
for fk in list(col.foreign_keys):
table.foreign_keys.remove(fk)
if fk.constraint in table.constraints:
# this might have been removed
# already, if it's a composite constraint
# and more than one col being replaced
table.constraints.remove(fk.constraint)
table._columns.replace(self)
if self.primary_key:
table.primary_key._replace(self)
Table._autoincrement_column._reset(table)
elif self.key in table.primary_key:
raise exc.ArgumentError(
"Trying to redefine primary-key column '%s' as a "
"non-primary-key column on table '%s'" % (
self.key, table.fullname))
self.table = table
if self.index:
if isinstance(self.index, basestring):
raise exc.ArgumentError(
"The 'index' keyword argument on Column is boolean only. "
"To create indexes with a specific name, create an "
"explicit Index object external to the Table.")
Index(expression._truncated_label('ix_%s' % self._label),
self, unique=bool(self.unique))
elif self.unique:
if isinstance(self.unique, basestring):
raise exc.ArgumentError(
"The 'unique' keyword argument on Column is boolean "
"only. To create unique constraints or indexes with a "
"specific name, append an explicit UniqueConstraint to "
"the Table's list of elements, or create an explicit "
"Index object external to the Table.")
table.append_constraint(UniqueConstraint(self.key))
def _on_table_attach(self, fn):
if self.table is not None:
fn(self, self.table)
event.listen(self, 'after_parent_attach', fn)
def copy(self, **kw):
"""Create a copy of this ``Column``, unitialized.
This is used in ``Table.tometadata``.
"""
# Constraint objects plus non-constraint-bound ForeignKey objects
args = \
[c.copy(**kw) for c in self.constraints] + \
[c.copy(**kw) for c in self.foreign_keys if not c.constraint]
type_ = self.type
if isinstance(type_, sqltypes.SchemaType):
type_ = type_.copy(**kw)
c = self._constructor(
name=self.name,
type_=type_,
key=self.key,
primary_key=self.primary_key,
nullable=self.nullable,
unique=self.unique,
system=self.system,
quote=self.quote,
index=self.index,
autoincrement=self.autoincrement,
default=self.default,
server_default=self.server_default,
onupdate=self.onupdate,
server_onupdate=self.server_onupdate,
info=self.info,
doc=self.doc,
*args
)
c.dispatch._update(self.dispatch)
return c
def _make_proxy(self, selectable, name=None, key=None,
name_is_truncatable=False, **kw):
"""Create a *proxy* for this column.
This is a copy of this ``Column`` referenced by a different parent
(such as an alias or select statement). The column should
be used only in select scenarios, as its full DDL/default
information is not transferred.
"""
fk = [ForeignKey(f.column, _constraint=f.constraint)
for f in self.foreign_keys]
if name is None and self.name is None:
raise exc.InvalidRequestError("Cannot initialize a sub-selectable"
" with this Column object until it's 'name' has "
"been assigned.")
try:
c = self._constructor(
expression._as_truncated(name or self.name) if \
name_is_truncatable else (name or self.name),
self.type,
key=key if key else name if name else self.key,
primary_key=self.primary_key,
nullable=self.nullable,
quote=self.quote,
_proxies=[self], *fk)
except TypeError, e:
# Py3K
#raise TypeError(
# "Could not create a copy of this %r object. "
# "Ensure the class includes a _constructor() "
# "attribute or method which accepts the "
# "standard Column constructor arguments, or "
# "references the Column class itself." % self.__class__) from e
# Py2K
raise TypeError(
"Could not create a copy of this %r object. "
"Ensure the class includes a _constructor() "
"attribute or method which accepts the "
"standard Column constructor arguments, or "
"references the Column class itself. "
"Original error: %s" % (self.__class__, e))
# end Py2K
c.table = selectable
selectable._columns.add(c)
if selectable._is_clone_of is not None:
c._is_clone_of = selectable._is_clone_of.columns[c.key]
if self.primary_key:
selectable.primary_key.add(c)
c.dispatch.after_parent_attach(c, selectable)
return c
def get_children(self, schema_visitor=False, **kwargs):
if schema_visitor:
return [x for x in (self.default, self.onupdate)
if x is not None] + \
list(self.foreign_keys) + list(self.constraints)
else:
return expression.ColumnClause.get_children(self, **kwargs)
class ForeignKey(SchemaItem):
"""Defines a dependency between two columns.
``ForeignKey`` is specified as an argument to a :class:`.Column` object,
e.g.::
t = Table("remote_table", metadata,
Column("remote_id", ForeignKey("main_table.id"))
)
Note that ``ForeignKey`` is only a marker object that defines
a dependency between two columns. The actual constraint
is in all cases represented by the :class:`.ForeignKeyConstraint`
object. This object will be generated automatically when
a ``ForeignKey`` is associated with a :class:`.Column` which
in turn is associated with a :class:`.Table`. Conversely,
when :class:`.ForeignKeyConstraint` is applied to a :class:`.Table`,
``ForeignKey`` markers are automatically generated to be
present on each associated :class:`.Column`, which are also
associated with the constraint object.
Note that you cannot define a "composite" foreign key constraint,
that is a constraint between a grouping of multiple parent/child
columns, using ``ForeignKey`` objects. To define this grouping,
the :class:`.ForeignKeyConstraint` object must be used, and applied
to the :class:`.Table`. The associated ``ForeignKey`` objects
are created automatically.
The ``ForeignKey`` objects associated with an individual
:class:`.Column` object are available in the `foreign_keys` collection
of that column.
Further examples of foreign key configuration are in
:ref:`metadata_foreignkeys`.
"""
__visit_name__ = 'foreign_key'
def __init__(self, column, _constraint=None, use_alter=False, name=None,
onupdate=None, ondelete=None, deferrable=None,
schema=None,
initially=None, link_to_name=False, match=None):
"""
Construct a column-level FOREIGN KEY.
The :class:`.ForeignKey` object when constructed generates a
:class:`.ForeignKeyConstraint` which is associated with the parent
:class:`.Table` object's collection of constraints.
:param column: A single target column for the key relationship. A
:class:`.Column` object or a column name as a string:
``tablename.columnkey`` or ``schema.tablename.columnkey``.
``columnkey`` is the ``key`` which has been assigned to the column
(defaults to the column name itself), unless ``link_to_name`` is
``True`` in which case the rendered name of the column is used.
.. versionadded:: 0.7.4
Note that if the schema name is not included, and the
underlying :class:`.MetaData` has a "schema", that value will
be used.
:param name: Optional string. An in-database name for the key if
`constraint` is not provided.
:param onupdate: Optional string. If set, emit ON UPDATE <value> when
issuing DDL for this constraint. Typical values include CASCADE,
DELETE and RESTRICT.
:param ondelete: Optional string. If set, emit ON DELETE <value> when
issuing DDL for this constraint. Typical values include CASCADE,
DELETE and RESTRICT.
:param deferrable: Optional bool. If set, emit DEFERRABLE or NOT
DEFERRABLE when issuing DDL for this constraint.
:param initially: Optional string. If set, emit INITIALLY <value> when
issuing DDL for this constraint.
:param link_to_name: if True, the string name given in ``column`` is
the rendered name of the referenced column, not its locally
assigned ``key``.
:param use_alter: passed to the underlying
:class:`.ForeignKeyConstraint` to indicate the constraint should be
generated/dropped externally from the CREATE TABLE/ DROP TABLE
statement. See that classes' constructor for details.
:param match: Optional string. If set, emit MATCH <value> when issuing
DDL for this constraint. Typical values include SIMPLE, PARTIAL
and FULL.
:param schema: Deprecated; this flag does nothing and will be removed
in 0.9.
"""
self._colspec = column
# the linked ForeignKeyConstraint.
# ForeignKey will create this when parent Column
# is attached to a Table, *or* ForeignKeyConstraint
# object passes itself in when creating ForeignKey
# markers.
self.constraint = _constraint
self.use_alter = use_alter
self.name = name
self.onupdate = onupdate
self.ondelete = ondelete
self.deferrable = deferrable
self.initially = initially
self.link_to_name = link_to_name
self.match = match
if schema:
util.warn_deprecated(
"'schema' argument on ForeignKey has no effect - "
"please specify the target as "
"<schemaname>.<tablename>.<colname>.")
def __repr__(self):
return "ForeignKey(%r)" % self._get_colspec()
def copy(self, schema=None):
"""Produce a copy of this :class:`.ForeignKey` object.
The new :class:`.ForeignKey` will not be bound
to any :class:`.Column`.
This method is usually used by the internal
copy procedures of :class:`.Column`, :class:`.Table`,
and :class:`.MetaData`.
:param schema: The returned :class:`.ForeignKey` will
reference the original table and column name, qualified
by the given string schema name.
"""
fk = ForeignKey(
self._get_colspec(schema=schema),
use_alter=self.use_alter,
name=self.name,
onupdate=self.onupdate,
ondelete=self.ondelete,
deferrable=self.deferrable,
initially=self.initially,
link_to_name=self.link_to_name,
match=self.match
)
fk.dispatch._update(self.dispatch)
return fk
def _get_colspec(self, schema=None):
"""Return a string based 'column specification' for this
:class:`.ForeignKey`.
This is usually the equivalent of the string-based "tablename.colname"
argument first passed to the object's constructor.
"""
if schema:
return schema + "." + self.column.table.name + \
"." + self.column.key
elif isinstance(self._colspec, basestring):
return self._colspec
elif hasattr(self._colspec, '__clause_element__'):
_column = self._colspec.__clause_element__()
else:
_column = self._colspec
return "%s.%s" % (_column.table.fullname, _column.key)
target_fullname = property(_get_colspec)
def references(self, table):
"""Return True if the given :class:`.Table` is referenced by this
:class:`.ForeignKey`."""
return table.corresponding_column(self.column) is not None
def get_referent(self, table):
"""Return the :class:`.Column` in the given :class:`.Table`
referenced by this :class:`.ForeignKey`.
Returns None if this :class:`.ForeignKey` does not reference the given
:class:`.Table`.
"""
return table.corresponding_column(self.column)
@util.memoized_property
def column(self):
"""Return the target :class:`.Column` referenced by this
:class:`.ForeignKey`.
If this :class:`.ForeignKey` was created using a
string-based target column specification, this
attribute will on first access initiate a resolution
process to locate the referenced remote
:class:`.Column`. The resolution process traverses
to the parent :class:`.Column`, :class:`.Table`, and
:class:`.MetaData` to proceed - if any of these aren't
yet present, an error is raised.
"""
# ForeignKey inits its remote column as late as possible, so tables
# can be defined without dependencies
if isinstance(self._colspec, basestring):
# locate the parent table this foreign key is attached to. we
# use the "original" column which our parent column represents
# (its a list of columns/other ColumnElements if the parent
# table is a UNION)
for c in self.parent.base_columns:
if isinstance(c, Column):
parenttable = c.table
break
else:
raise exc.ArgumentError(
"Parent column '%s' does not descend from a "
"table-attached Column" % str(self.parent))
m = self._colspec.split('.')
if m is None:
raise exc.ArgumentError(
"Invalid foreign key column specification: %s" %
self._colspec)
# A FK between column 'bar' and table 'foo' can be
# specified as 'foo', 'foo.bar', 'dbo.foo.bar',
# 'otherdb.dbo.foo.bar'. Once we have the column name and
# the table name, treat everything else as the schema
# name. Some databases (e.g. Sybase) support
# inter-database foreign keys. See tickets#1341 and --
# indirectly related -- Ticket #594. This assumes that '.'
# will never appear *within* any component of the FK.
(schema, tname, colname) = (None, None, None)
if schema is None and parenttable.metadata.schema is not None:
schema = parenttable.metadata.schema
if (len(m) == 1):
tname = m.pop()
else:
colname = m.pop()
tname = m.pop()
if (len(m) > 0):
schema = '.'.join(m)
if _get_table_key(tname, schema) not in parenttable.metadata:
raise exc.NoReferencedTableError(
"Foreign key associated with column '%s' could not find "
"table '%s' with which to generate a "
"foreign key to target column '%s'" %
(self.parent, tname, colname),
tname)
table = Table(tname, parenttable.metadata,
mustexist=True, schema=schema)
if not hasattr(self.constraint, '_referred_table'):
self.constraint._referred_table = table
elif self.constraint._referred_table is not table:
raise exc.ArgumentError(
'ForeignKeyConstraint on %s(%s) refers to '
'multiple remote tables: %s and %s' % (
parenttable,
self.constraint._col_description,
self.constraint._referred_table,
table
))
_column = None
if colname is None:
# colname is None in the case that ForeignKey argument
# was specified as table name only, in which case we
# match the column name to the same column on the
# parent.
key = self.parent
_column = table.c.get(self.parent.key, None)
elif self.link_to_name:
key = colname
for c in table.c:
if c.name == colname:
_column = c
else:
key = colname
_column = table.c.get(colname, None)
if _column is None:
raise exc.NoReferencedColumnError(
"Could not create ForeignKey '%s' on table '%s': "
"table '%s' has no column named '%s'" % (
self._colspec, parenttable.name, table.name, key),
table.name, key)
elif hasattr(self._colspec, '__clause_element__'):
_column = self._colspec.__clause_element__()
else:
_column = self._colspec
# propagate TypeEngine to parent if it didn't have one
if isinstance(self.parent.type, sqltypes.NullType):
self.parent.type = _column.type
return _column
def _set_parent(self, column):
if hasattr(self, 'parent'):
if self.parent is column:
return
raise exc.InvalidRequestError(
"This ForeignKey already has a parent !")
self.parent = column
self.parent.foreign_keys.add(self)
self.parent._on_table_attach(self._set_table)
def _set_table(self, column, table):
# standalone ForeignKey - create ForeignKeyConstraint
# on the hosting Table when attached to the Table.
if self.constraint is None and isinstance(table, Table):
self.constraint = ForeignKeyConstraint(
[], [], use_alter=self.use_alter, name=self.name,
onupdate=self.onupdate, ondelete=self.ondelete,
deferrable=self.deferrable, initially=self.initially,
match=self.match,
)
self.constraint._elements[self.parent] = self
self.constraint._set_parent_with_dispatch(table)
table.foreign_keys.add(self)
class _NotAColumnExpr(object):
def _not_a_column_expr(self):
raise exc.InvalidRequestError(
"This %s cannot be used directly "
"as a column expression." % self.__class__.__name__)
__clause_element__ = self_group = lambda self: self._not_a_column_expr()
_from_objects = property(lambda self: self._not_a_column_expr())
class DefaultGenerator(_NotAColumnExpr, SchemaItem):
"""Base class for column *default* values."""
__visit_name__ = 'default_generator'
is_sequence = False
is_server_default = False
column = None
def __init__(self, for_update=False):
self.for_update = for_update
def _set_parent(self, column):
self.column = column
if self.for_update:
self.column.onupdate = self
else:
self.column.default = self
def execute(self, bind=None, **kwargs):
if bind is None:
bind = _bind_or_error(self)
return bind._execute_default(self, **kwargs)
@property
def bind(self):
"""Return the connectable associated with this default."""
if getattr(self, 'column', None) is not None:
return self.column.table.bind
else:
return None
class ColumnDefault(DefaultGenerator):
"""A plain default value on a column.
This could correspond to a constant, a callable function,
or a SQL clause.
:class:`.ColumnDefault` is generated automatically
whenever the ``default``, ``onupdate`` arguments of
:class:`.Column` are used. A :class:`.ColumnDefault`
can be passed positionally as well.
For example, the following::
Column('foo', Integer, default=50)
Is equivalent to::
Column('foo', Integer, ColumnDefault(50))
"""
def __init__(self, arg, **kwargs):
""""Construct a new :class:`.ColumnDefault`.
:param arg: argument representing the default value.
May be one of the following:
* a plain non-callable Python value, such as a
string, integer, boolean, or other simple type.
The default value will be used as is each time.
* a SQL expression, that is one which derives from
:class:`.ColumnElement`. The SQL expression will
be rendered into the INSERT or UPDATE statement,
or in the case of a primary key column when
RETURNING is not used may be
pre-executed before an INSERT within a SELECT.
* A Python callable. The function will be invoked for each
new row subject to an INSERT or UPDATE.
The callable must accept exactly
zero or one positional arguments. The one-argument form
will receive an instance of the :class:`.ExecutionContext`,
which provides contextual information as to the current
:class:`.Connection` in use as well as the current
statement and parameters.
"""
super(ColumnDefault, self).__init__(**kwargs)
if isinstance(arg, FetchedValue):
raise exc.ArgumentError(
"ColumnDefault may not be a server-side default type.")
if util.callable(arg):
arg = self._maybe_wrap_callable(arg)
self.arg = arg
@util.memoized_property
def is_callable(self):
return util.callable(self.arg)
@util.memoized_property
def is_clause_element(self):
return isinstance(self.arg, expression.ClauseElement)
@util.memoized_property
def is_scalar(self):
return not self.is_callable and \
not self.is_clause_element and \
not self.is_sequence
def _maybe_wrap_callable(self, fn):
"""Wrap callables that don't accept a context.
The alternative here is to require that
a simple callable passed to "default" would need
to be of the form "default=lambda ctx: datetime.now".
That is the more "correct" way to go, but the case
of using a zero-arg callable for "default" is so
much more prominent than the context-specific one
I'm having trouble justifying putting that inconvenience
on everyone.
"""
if inspect.isfunction(fn):
inspectable = fn
elif inspect.isclass(fn):
inspectable = fn.__init__
elif hasattr(fn, '__call__'):
inspectable = fn.__call__
else:
# probably not inspectable, try anyways.
inspectable = fn
try:
argspec = inspect.getargspec(inspectable)
except TypeError:
return lambda ctx: fn()
defaulted = argspec[3] is not None and len(argspec[3]) or 0
positionals = len(argspec[0]) - defaulted
# Py3K compat - no unbound methods
if inspect.ismethod(inspectable) or inspect.isclass(fn):
positionals -= 1
if positionals == 0:
return lambda ctx: fn()
elif positionals == 1:
return fn
else:
raise exc.ArgumentError(
"ColumnDefault Python function takes zero or one "
"positional arguments")
def _visit_name(self):
if self.for_update:
return "column_onupdate"
else:
return "column_default"
__visit_name__ = property(_visit_name)
def __repr__(self):
return "ColumnDefault(%r)" % self.arg
class Sequence(DefaultGenerator):
"""Represents a named database sequence.
The :class:`.Sequence` object represents the name and configurational
parameters of a database sequence. It also represents
a construct that can be "executed" by a SQLAlchemy :class:`.Engine`
or :class:`.Connection`, rendering the appropriate "next value" function
for the target database and returning a result.
The :class:`.Sequence` is typically associated with a primary key column::
some_table = Table('some_table', metadata,
Column('id', Integer, Sequence('some_table_seq'), primary_key=True)
)
When CREATE TABLE is emitted for the above :class:`.Table`, if the
target platform supports sequences, a CREATE SEQUENCE statement will
be emitted as well. For platforms that don't support sequences,
the :class:`.Sequence` construct is ignored.
.. seealso::
:class:`.CreateSequence`
:class:`.DropSequence`
"""
__visit_name__ = 'sequence'
is_sequence = True
def __init__(self, name, start=None, increment=None, schema=None,
optional=False, quote=None, metadata=None,
quote_schema=None,
for_update=False):
"""Construct a :class:`.Sequence` object.
:param name: The name of the sequence.
:param start: the starting index of the sequence. This value is
used when the CREATE SEQUENCE command is emitted to the database
as the value of the "START WITH" clause. If ``None``, the
clause is omitted, which on most platforms indicates a starting
value of 1.
:param increment: the increment value of the sequence. This
value is used when the CREATE SEQUENCE command is emitted to
the database as the value of the "INCREMENT BY" clause. If ``None``,
the clause is omitted, which on most platforms indicates an
increment of 1.
:param schema: Optional schema name for the sequence, if located
in a schema other than the default.
:param optional: boolean value, when ``True``, indicates that this
:class:`.Sequence` object only needs to be explicitly generated
on backends that don't provide another way to generate primary
key identifiers. Currently, it essentially means, "don't create
this sequence on the Postgresql backend, where the SERIAL keyword
creates a sequence for us automatically".
:param quote: boolean value, when ``True`` or ``False``, explicitly
forces quoting of the schema name on or off. When left at its
default of ``None``, normal quoting rules based on casing and reserved
words take place.
:param metadata: optional :class:`.MetaData` object which will be
associated with this :class:`.Sequence`. A :class:`.Sequence`
that is associated with a :class:`.MetaData` gains access to the
``bind`` of that :class:`.MetaData`, meaning the
:meth:`.Sequence.create` and :meth:`.Sequence.drop` methods will
make usage of that engine automatically.
.. versionchanged:: 0.7
Additionally, the appropriate CREATE SEQUENCE/
DROP SEQUENCE DDL commands will be emitted corresponding to this
:class:`.Sequence` when :meth:`.MetaData.create_all` and
:meth:`.MetaData.drop_all` are invoked.
Note that when a :class:`.Sequence` is applied to a :class:`.Column`,
the :class:`.Sequence` is automatically associated with the
:class:`.MetaData` object of that column's parent :class:`.Table`,
when that association is made. The :class:`.Sequence` will then
be subject to automatic CREATE SEQUENCE/DROP SEQUENCE corresponding
to when the :class:`.Table` object itself is created or dropped,
rather than that of the :class:`.MetaData` object overall.
:param for_update: Indicates this :class:`.Sequence`, when associated
with a :class:`.Column`, should be invoked for UPDATE statements
on that column's table, rather than for INSERT statements, when
no value is otherwise present for that column in the statement.
"""
super(Sequence, self).__init__(for_update=for_update)
self.name = name
self.start = start
self.increment = increment
self.optional = optional
self.quote = quote
if metadata is not None and schema is None and metadata.schema:
self.schema = schema = metadata.schema
self.quote_schema = metadata.quote_schema
else:
self.schema = schema
self.quote_schema = quote_schema
self.metadata = metadata
self._key = _get_table_key(name, schema)
if metadata:
self._set_metadata(metadata)
@util.memoized_property
def is_callable(self):
return False
@util.memoized_property
def is_clause_element(self):
return False
def next_value(self):
"""Return a :class:`.next_value` function element
which will render the appropriate increment function
for this :class:`.Sequence` within any SQL expression.
"""
return expression.func.next_value(self, bind=self.bind)
def _set_parent(self, column):
super(Sequence, self)._set_parent(column)
column._on_table_attach(self._set_table)
def _set_table(self, column, table):
self._set_metadata(table.metadata)
def _set_metadata(self, metadata):
self.metadata = metadata
self.metadata._sequences[self._key] = self
@property
def bind(self):
if self.metadata:
return self.metadata.bind
else:
return None
def create(self, bind=None, checkfirst=True):
"""Creates this sequence in the database."""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaGenerator,
self,
checkfirst=checkfirst)
def drop(self, bind=None, checkfirst=True):
"""Drops this sequence from the database."""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaDropper,
self,
checkfirst=checkfirst)
def _not_a_column_expr(self):
raise exc.InvalidRequestError(
"This %s cannot be used directly "
"as a column expression. Use func.next_value(sequence) "
"to produce a 'next value' function that's usable "
"as a column element."
% self.__class__.__name__)
class FetchedValue(_NotAColumnExpr, events.SchemaEventTarget):
"""A marker for a transparent database-side default.
Use :class:`.FetchedValue` when the database is configured
to provide some automatic default for a column.
E.g.::
Column('foo', Integer, FetchedValue())
Would indicate that some trigger or default generator
will create a new value for the ``foo`` column during an
INSERT.
.. seealso::
:ref:`triggered_columns`
"""
is_server_default = True
reflected = False
has_argument = False
def __init__(self, for_update=False):
self.for_update = for_update
def _as_for_update(self, for_update):
if for_update == self.for_update:
return self
else:
return self._clone(for_update)
def _clone(self, for_update):
n = self.__class__.__new__(self.__class__)
n.__dict__.update(self.__dict__)
n.__dict__.pop('column', None)
n.for_update = for_update
return n
def _set_parent(self, column):
self.column = column
if self.for_update:
self.column.server_onupdate = self
else:
self.column.server_default = self
def __repr__(self):
return util.generic_repr(self)
inspection._self_inspects(FetchedValue)
class DefaultClause(FetchedValue):
"""A DDL-specified DEFAULT column value.
:class:`.DefaultClause` is a :class:`.FetchedValue`
that also generates a "DEFAULT" clause when
"CREATE TABLE" is emitted.
:class:`.DefaultClause` is generated automatically
whenever the ``server_default``, ``server_onupdate`` arguments of
:class:`.Column` are used. A :class:`.DefaultClause`
can be passed positionally as well.
For example, the following::
Column('foo', Integer, server_default="50")
Is equivalent to::
Column('foo', Integer, DefaultClause("50"))
"""
has_argument = True
def __init__(self, arg, for_update=False, _reflected=False):
util.assert_arg_type(arg, (basestring,
expression.ClauseElement,
expression.TextClause), 'arg')
super(DefaultClause, self).__init__(for_update)
self.arg = arg
self.reflected = _reflected
def __repr__(self):
return "DefaultClause(%r, for_update=%r)" % \
(self.arg, self.for_update)
class PassiveDefault(DefaultClause):
"""A DDL-specified DEFAULT column value.
.. deprecated:: 0.6
:class:`.PassiveDefault` is deprecated.
Use :class:`.DefaultClause`.
"""
@util.deprecated("0.6",
":class:`.PassiveDefault` is deprecated. "
"Use :class:`.DefaultClause`.",
False)
def __init__(self, *arg, **kw):
DefaultClause.__init__(self, *arg, **kw)
class Constraint(SchemaItem):
"""A table-level SQL constraint."""
__visit_name__ = 'constraint'
def __init__(self, name=None, deferrable=None, initially=None,
_create_rule=None,
**kw):
"""Create a SQL constraint.
:param name:
Optional, the in-database name of this ``Constraint``.
:param deferrable:
Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when
issuing DDL for this constraint.
:param initially:
Optional string. If set, emit INITIALLY <value> when issuing DDL
for this constraint.
:param _create_rule:
a callable which is passed the DDLCompiler object during
compilation. Returns True or False to signal inline generation of
this Constraint.
The AddConstraint and DropConstraint DDL constructs provide
DDLElement's more comprehensive "conditional DDL" approach that is
passed a database connection when DDL is being issued. _create_rule
is instead called during any CREATE TABLE compilation, where there
may not be any transaction/connection in progress. However, it
allows conditional compilation of the constraint even for backends
which do not support addition of constraints through ALTER TABLE,
which currently includes SQLite.
_create_rule is used by some types to create constraints.
Currently, its call signature is subject to change at any time.
:param \**kwargs:
Dialect-specific keyword parameters, see the documentation
for various dialects and constraints regarding options here.
"""
self.name = name
self.deferrable = deferrable
self.initially = initially
self._create_rule = _create_rule
util.set_creation_order(self)
_validate_dialect_kwargs(kw, self.__class__.__name__)
self.kwargs = kw
@property
def table(self):
try:
if isinstance(self.parent, Table):
return self.parent
except AttributeError:
pass
raise exc.InvalidRequestError(
"This constraint is not bound to a table. Did you "
"mean to call table.append_constraint(constraint) ?")
def _set_parent(self, parent):
self.parent = parent
parent.constraints.add(self)
def copy(self, **kw):
raise NotImplementedError()
class ColumnCollectionMixin(object):
def __init__(self, *columns):
self.columns = expression.ColumnCollection()
self._pending_colargs = [_to_schema_column_or_string(c)
for c in columns]
if self._pending_colargs and \
isinstance(self._pending_colargs[0], Column) and \
isinstance(self._pending_colargs[0].table, Table):
self._set_parent_with_dispatch(self._pending_colargs[0].table)
def _set_parent(self, table):
for col in self._pending_colargs:
if isinstance(col, basestring):
col = table.c[col]
self.columns.add(col)
class ColumnCollectionConstraint(ColumnCollectionMixin, Constraint):
"""A constraint that proxies a ColumnCollection."""
def __init__(self, *columns, **kw):
"""
:param \*columns:
A sequence of column names or Column objects.
:param name:
Optional, the in-database name of this constraint.
:param deferrable:
Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when
issuing DDL for this constraint.
:param initially:
Optional string. If set, emit INITIALLY <value> when issuing DDL
for this constraint.
"""
ColumnCollectionMixin.__init__(self, *columns)
Constraint.__init__(self, **kw)
def _set_parent(self, table):
ColumnCollectionMixin._set_parent(self, table)
Constraint._set_parent(self, table)
def __contains__(self, x):
return x in self.columns
def copy(self, **kw):
c = self.__class__(name=self.name, deferrable=self.deferrable,
initially=self.initially, *self.columns.keys())
c.dispatch._update(self.dispatch)
return c
def contains_column(self, col):
return self.columns.contains_column(col)
def __iter__(self):
# inlining of
# return iter(self.columns)
# ColumnCollection->OrderedProperties->OrderedDict
ordered_dict = self.columns._data
return (ordered_dict[key] for key in ordered_dict._list)
def __len__(self):
return len(self.columns._data)
class CheckConstraint(Constraint):
"""A table- or column-level CHECK constraint.
Can be included in the definition of a Table or Column.
"""
def __init__(self, sqltext, name=None, deferrable=None,
initially=None, table=None, _create_rule=None,
_autoattach=True):
"""Construct a CHECK constraint.
:param sqltext:
A string containing the constraint definition, which will be used
verbatim, or a SQL expression construct.
:param name:
Optional, the in-database name of the constraint.
:param deferrable:
Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when
issuing DDL for this constraint.
:param initially:
Optional string. If set, emit INITIALLY <value> when issuing DDL
for this constraint.
"""
super(CheckConstraint, self).\
__init__(name, deferrable, initially, _create_rule)
self.sqltext = expression._literal_as_text(sqltext)
if table is not None:
self._set_parent_with_dispatch(table)
elif _autoattach:
cols = sqlutil.find_columns(self.sqltext)
tables = set([c.table for c in cols
if isinstance(c.table, Table)])
if len(tables) == 1:
self._set_parent_with_dispatch(
tables.pop())
def __visit_name__(self):
if isinstance(self.parent, Table):
return "check_constraint"
else:
return "column_check_constraint"
__visit_name__ = property(__visit_name__)
def copy(self, target_table=None, **kw):
if target_table is not None:
def replace(col):
if self.table.c.contains_column(col):
return target_table.c[col.key]
else:
return None
sqltext = visitors.replacement_traverse(self.sqltext, {}, replace)
else:
sqltext = self.sqltext
c = CheckConstraint(sqltext,
name=self.name,
initially=self.initially,
deferrable=self.deferrable,
_create_rule=self._create_rule,
table=target_table,
_autoattach=False)
c.dispatch._update(self.dispatch)
return c
class ForeignKeyConstraint(Constraint):
"""A table-level FOREIGN KEY constraint.
Defines a single column or composite FOREIGN KEY ... REFERENCES
constraint. For a no-frills, single column foreign key, adding a
:class:`.ForeignKey` to the definition of a :class:`.Column` is a shorthand
equivalent for an unnamed, single column :class:`.ForeignKeyConstraint`.
Examples of foreign key configuration are in :ref:`metadata_foreignkeys`.
"""
__visit_name__ = 'foreign_key_constraint'
def __init__(self, columns, refcolumns, name=None, onupdate=None,
ondelete=None, deferrable=None, initially=None, use_alter=False,
link_to_name=False, match=None, table=None):
"""Construct a composite-capable FOREIGN KEY.
:param columns: A sequence of local column names. The named columns
must be defined and present in the parent Table. The names should
match the ``key`` given to each column (defaults to the name) unless
``link_to_name`` is True.
:param refcolumns: A sequence of foreign column names or Column
objects. The columns must all be located within the same Table.
:param name: Optional, the in-database name of the key.
:param onupdate: Optional string. If set, emit ON UPDATE <value> when
issuing DDL for this constraint. Typical values include CASCADE,
DELETE and RESTRICT.
:param ondelete: Optional string. If set, emit ON DELETE <value> when
issuing DDL for this constraint. Typical values include CASCADE,
DELETE and RESTRICT.
:param deferrable: Optional bool. If set, emit DEFERRABLE or NOT
DEFERRABLE when issuing DDL for this constraint.
:param initially: Optional string. If set, emit INITIALLY <value> when
issuing DDL for this constraint.
:param link_to_name: if True, the string name given in ``column`` is
the rendered name of the referenced column, not its locally assigned
``key``.
:param use_alter: If True, do not emit the DDL for this constraint as
part of the CREATE TABLE definition. Instead, generate it via an
ALTER TABLE statement issued after the full collection of tables
have been created, and drop it via an ALTER TABLE statement before
the full collection of tables are dropped. This is shorthand for the
usage of :class:`.AddConstraint` and :class:`.DropConstraint` applied
as "after-create" and "before-drop" events on the MetaData object.
This is normally used to generate/drop constraints on objects that
are mutually dependent on each other.
:param match: Optional string. If set, emit MATCH <value> when issuing
DDL for this constraint. Typical values include SIMPLE, PARTIAL
and FULL.
"""
super(ForeignKeyConstraint, self).\
__init__(name, deferrable, initially)
self.onupdate = onupdate
self.ondelete = ondelete
self.link_to_name = link_to_name
if self.name is None and use_alter:
raise exc.ArgumentError("Alterable Constraint requires a name")
self.use_alter = use_alter
self.match = match
self._elements = util.OrderedDict()
# standalone ForeignKeyConstraint - create
# associated ForeignKey objects which will be applied to hosted
# Column objects (in col.foreign_keys), either now or when attached
# to the Table for string-specified names
for col, refcol in zip(columns, refcolumns):
self._elements[col] = ForeignKey(
refcol,
_constraint=self,
name=self.name,
onupdate=self.onupdate,
ondelete=self.ondelete,
use_alter=self.use_alter,
link_to_name=self.link_to_name,
match=self.match
)
if table is not None:
self._set_parent_with_dispatch(table)
elif columns and \
isinstance(columns[0], Column) and \
columns[0].table is not None:
self._set_parent_with_dispatch(columns[0].table)
@property
def _col_description(self):
return ", ".join(self._elements)
@property
def columns(self):
return self._elements.keys()
@property
def elements(self):
return self._elements.values()
def _set_parent(self, table):
super(ForeignKeyConstraint, self)._set_parent(table)
for col, fk in self._elements.iteritems():
# string-specified column names now get
# resolved to Column objects
if isinstance(col, basestring):
try:
col = table.c[col]
except KeyError:
raise exc.ArgumentError(
"Can't create ForeignKeyConstraint "
"on table '%s': no column "
"named '%s' is present." % (table.description, col))
if not hasattr(fk, 'parent') or \
fk.parent is not col:
fk._set_parent_with_dispatch(col)
if self.use_alter:
def supports_alter(ddl, event, schema_item, bind, **kw):
return table in set(kw['tables']) and \
bind.dialect.supports_alter
event.listen(table.metadata, "after_create",
AddConstraint(self, on=supports_alter))
event.listen(table.metadata, "before_drop",
DropConstraint(self, on=supports_alter))
def copy(self, schema=None, **kw):
fkc = ForeignKeyConstraint(
[x.parent.key for x in self._elements.values()],
[x._get_colspec(schema=schema) for x in self._elements.values()],
name=self.name,
onupdate=self.onupdate,
ondelete=self.ondelete,
use_alter=self.use_alter,
deferrable=self.deferrable,
initially=self.initially,
link_to_name=self.link_to_name,
match=self.match
)
fkc.dispatch._update(self.dispatch)
return fkc
class PrimaryKeyConstraint(ColumnCollectionConstraint):
"""A table-level PRIMARY KEY constraint.
Defines a single column or composite PRIMARY KEY constraint. For a
no-frills primary key, adding ``primary_key=True`` to one or more
``Column`` definitions is a shorthand equivalent for an unnamed single- or
multiple-column PrimaryKeyConstraint.
"""
__visit_name__ = 'primary_key_constraint'
def _set_parent(self, table):
super(PrimaryKeyConstraint, self)._set_parent(table)
if table.primary_key in table.constraints:
table.constraints.remove(table.primary_key)
table.primary_key = self
table.constraints.add(self)
for c in self.columns:
c.primary_key = True
def _replace(self, col):
self.columns.replace(col)
class UniqueConstraint(ColumnCollectionConstraint):
"""A table-level UNIQUE constraint.
Defines a single column or composite UNIQUE constraint. For a no-frills,
single column constraint, adding ``unique=True`` to the ``Column``
definition is a shorthand equivalent for an unnamed, single column
UniqueConstraint.
"""
__visit_name__ = 'unique_constraint'
class Index(ColumnCollectionMixin, SchemaItem):
"""A table-level INDEX.
Defines a composite (one or more column) INDEX.
E.g.::
sometable = Table("sometable", metadata,
Column("name", String(50)),
Column("address", String(100))
)
Index("some_index", sometable.c.name)
For a no-frills, single column index, adding
:class:`.Column` also supports ``index=True``::
sometable = Table("sometable", metadata,
Column("name", String(50), index=True)
)
For a composite index, multiple columns can be specified::
Index("some_index", sometable.c.name, sometable.c.address)
Functional indexes are supported as well, keeping in mind that at least
one :class:`.Column` must be present::
Index("some_index", func.lower(sometable.c.name))
.. versionadded:: 0.8 support for functional and expression-based indexes.
.. seealso::
:ref:`schema_indexes` - General information on :class:`.Index`.
:ref:`postgresql_indexes` - PostgreSQL-specific options available for the
:class:`.Index` construct.
:ref:`mysql_indexes` - MySQL-specific options available for the
:class:`.Index` construct.
:ref:`mssql_indexes` - MSSQL-specific options available for the
:class:`.Index` construct.
"""
__visit_name__ = 'index'
def __init__(self, name, *expressions, **kw):
"""Construct an index object.
:param name:
The name of the index
:param \*expressions:
Column or SQL expressions.
:param unique:
Defaults to False: create a unique index.
:param \**kw:
Other keyword arguments may be interpreted by specific dialects.
"""
self.table = None
columns = []
for expr in expressions:
if not isinstance(expr, expression.ClauseElement):
columns.append(expr)
else:
cols = []
visitors.traverse(expr, {}, {'column': cols.append})
if cols:
columns.append(cols[0])
else:
columns.append(expr)
self.expressions = expressions
# will call _set_parent() if table-bound column
# objects are present
ColumnCollectionMixin.__init__(self, *columns)
self.name = name
self.unique = kw.pop('unique', False)
self.kwargs = kw
def _set_parent(self, table):
ColumnCollectionMixin._set_parent(self, table)
if self.table is not None and table is not self.table:
raise exc.ArgumentError(
"Index '%s' is against table '%s', and "
"cannot be associated with table '%s'." % (
self.name,
self.table.description,
table.description
)
)
self.table = table
for c in self.columns:
if c.table != self.table:
raise exc.ArgumentError(
"Column '%s' is not part of table '%s'." %
(c, self.table.description)
)
table.indexes.add(self)
self.expressions = [
expr if isinstance(expr, expression.ClauseElement)
else colexpr
for expr, colexpr in zip(self.expressions, self.columns)
]
@property
def bind(self):
"""Return the connectable associated with this Index."""
return self.table.bind
def create(self, bind=None):
"""Issue a ``CREATE`` statement for this
:class:`.Index`, using the given :class:`.Connectable`
for connectivity.
.. seealso::
:meth:`.MetaData.create_all`.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaGenerator, self)
return self
def drop(self, bind=None):
"""Issue a ``DROP`` statement for this
:class:`.Index`, using the given :class:`.Connectable`
for connectivity.
.. seealso::
:meth:`.MetaData.drop_all`.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaDropper, self)
def __repr__(self):
return 'Index(%s)' % (
", ".join(
[repr(self.name)] +
[repr(c) for c in self.columns] +
(self.unique and ["unique=True"] or [])
))
class MetaData(SchemaItem):
"""A collection of :class:`.Table` objects and their associated schema
constructs.
Holds a collection of :class:`.Table` objects as well as
an optional binding to an :class:`.Engine` or
:class:`.Connection`. If bound, the :class:`.Table` objects
in the collection and their columns may participate in implicit SQL
execution.
The :class:`.Table` objects themselves are stored in the
``metadata.tables`` dictionary.
The ``bind`` property may be assigned to dynamically. A common pattern is
to start unbound and then bind later when an engine is available::
metadata = MetaData()
# define tables
Table('mytable', metadata, ...)
# connect to an engine later, perhaps after loading a URL from a
# configuration file
metadata.bind = an_engine
MetaData is a thread-safe object after tables have been explicitly defined
or loaded via reflection.
.. seealso::
:ref:`metadata_describing` - Introduction to database metadata
"""
__visit_name__ = 'metadata'
def __init__(self, bind=None, reflect=False, schema=None,
quote_schema=None):
"""Create a new MetaData object.
:param bind:
An Engine or Connection to bind to. May also be a string or URL
instance, these are passed to create_engine() and this MetaData will
be bound to the resulting engine.
:param reflect:
Optional, automatically load all tables from the bound database.
Defaults to False. ``bind`` is required when this option is set.
.. deprecated:: 0.8
Please use the :meth:`.MetaData.reflect` method.
:param schema:
The default schema to use for the :class:`.Table`,
:class:`.Sequence`, and other objects associated with this
:class:`.MetaData`. Defaults to ``None``.
:param quote_schema:
Sets the ``quote_schema`` flag for those :class:`.Table`,
:class:`.Sequence`, and other objects which make usage of the
local ``schema`` name.
.. versionadded:: 0.7.4
``schema`` and ``quote_schema`` parameters.
"""
self.tables = util.immutabledict()
self.schema = schema
self.quote_schema = quote_schema
self._schemas = set()
self._sequences = {}
self.bind = bind
if reflect:
util.warn("reflect=True is deprecate; please "
"use the reflect() method.")
if not bind:
raise exc.ArgumentError(
"A bind must be supplied in conjunction "
"with reflect=True")
self.reflect()
def __repr__(self):
return 'MetaData(bind=%r)' % self.bind
def __contains__(self, table_or_key):
if not isinstance(table_or_key, basestring):
table_or_key = table_or_key.key
return table_or_key in self.tables
def _add_table(self, name, schema, table):
key = _get_table_key(name, schema)
dict.__setitem__(self.tables, key, table)
if schema:
self._schemas.add(schema)
def _remove_table(self, name, schema):
key = _get_table_key(name, schema)
dict.pop(self.tables, key, None)
if self._schemas:
self._schemas = set([t.schema
for t in self.tables.values()
if t.schema is not None])
def __getstate__(self):
return {'tables': self.tables,
'schema': self.schema,
'quote_schema': self.quote_schema,
'schemas': self._schemas,
'sequences': self._sequences}
def __setstate__(self, state):
self.tables = state['tables']
self.schema = state['schema']
self.quote_schema = state['quote_schema']
self._bind = None
self._sequences = state['sequences']
self._schemas = state['schemas']
def is_bound(self):
"""True if this MetaData is bound to an Engine or Connection."""
return self._bind is not None
def bind(self):
"""An :class:`.Engine` or :class:`.Connection` to which this
:class:`.MetaData` is bound.
Typically, a :class:`.Engine` is assigned to this attribute
so that "implicit execution" may be used, or alternatively
as a means of providing engine binding information to an
ORM :class:`.Session` object::
engine = create_engine("someurl://")
metadata.bind = engine
.. seealso::
:ref:`dbengine_implicit` - background on "bound metadata"
"""
return self._bind
def _bind_to(self, bind):
"""Bind this MetaData to an Engine, Connection, string or URL."""
if isinstance(bind, (basestring, url.URL)):
from sqlalchemy import create_engine
self._bind = create_engine(bind)
else:
self._bind = bind
bind = property(bind, _bind_to)
def clear(self):
"""Clear all Table objects from this MetaData."""
dict.clear(self.tables)
self._schemas.clear()
def remove(self, table):
"""Remove the given Table object from this MetaData."""
self._remove_table(table.name, table.schema)
@property
def sorted_tables(self):
"""Returns a list of :class:`.Table` objects sorted in order of
foreign key dependency.
The sorting will place :class:`.Table` objects that have dependencies
first, before the dependencies themselves, representing the
order in which they can be created. To get the order in which
the tables would be dropped, use the ``reversed()`` Python built-in.
.. seealso::
:meth:`.Inspector.sorted_tables`
"""
return sqlutil.sort_tables(self.tables.itervalues())
def reflect(self, bind=None, schema=None, views=False, only=None):
"""Load all available table definitions from the database.
Automatically creates ``Table`` entries in this ``MetaData`` for any
table available in the database but not yet present in the
``MetaData``. May be called multiple times to pick up tables recently
added to the database, however no special action is taken if a table
in this ``MetaData`` no longer exists in the database.
:param bind:
A :class:`.Connectable` used to access the database; if None, uses
the existing bind on this ``MetaData``, if any.
:param schema:
Optional, query and reflect tables from an alterate schema.
If None, the schema associated with this :class:`.MetaData`
is used, if any.
:param views:
If True, also reflect views.
:param only:
Optional. Load only a sub-set of available named tables. May be
specified as a sequence of names or a callable.
If a sequence of names is provided, only those tables will be
reflected. An error is raised if a table is requested but not
available. Named tables already present in this ``MetaData`` are
ignored.
If a callable is provided, it will be used as a boolean predicate to
filter the list of potential table names. The callable is called
with a table name and this ``MetaData`` instance as positional
arguments and should return a true value for any table to reflect.
"""
if bind is None:
bind = _bind_or_error(self)
with bind.connect() as conn:
reflect_opts = {
'autoload': True,
'autoload_with': conn
}
if schema is None:
schema = self.schema
if schema is not None:
reflect_opts['schema'] = schema
available = util.OrderedSet(bind.engine.table_names(schema,
connection=conn))
if views:
available.update(
bind.dialect.get_view_names(conn, schema)
)
if schema is not None:
available_w_schema = util.OrderedSet(["%s.%s" % (schema, name)
for name in available])
else:
available_w_schema = available
current = set(self.tables)
if only is None:
load = [name for name, schname in
zip(available, available_w_schema)
if schname not in current]
elif util.callable(only):
load = [name for name, schname in
zip(available, available_w_schema)
if schname not in current and only(name, self)]
else:
missing = [name for name in only if name not in available]
if missing:
s = schema and (" schema '%s'" % schema) or ''
raise exc.InvalidRequestError(
'Could not reflect: requested table(s) not available '
'in %s%s: (%s)' %
(bind.engine.url, s, ', '.join(missing)))
load = [name for name in only if name not in current]
for name in load:
Table(name, self, **reflect_opts)
def append_ddl_listener(self, event_name, listener):
"""Append a DDL event listener to this ``MetaData``.
Deprecated. See :class:`.DDLEvents`.
"""
def adapt_listener(target, connection, **kw):
tables = kw['tables']
listener(event, target, connection, tables=tables)
event.listen(self, "" + event_name.replace('-', '_'), adapt_listener)
def create_all(self, bind=None, tables=None, checkfirst=True):
"""Create all tables stored in this metadata.
Conditional by default, will not attempt to recreate tables already
present in the target database.
:param bind:
A :class:`.Connectable` used to access the
database; if None, uses the existing bind on this ``MetaData``, if
any.
:param tables:
Optional list of ``Table`` objects, which is a subset of the total
tables in the ``MetaData`` (others are ignored).
:param checkfirst:
Defaults to True, don't issue CREATEs for tables already present
in the target database.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaGenerator,
self,
checkfirst=checkfirst,
tables=tables)
def drop_all(self, bind=None, tables=None, checkfirst=True):
"""Drop all tables stored in this metadata.
Conditional by default, will not attempt to drop tables not present in
the target database.
:param bind:
A :class:`.Connectable` used to access the
database; if None, uses the existing bind on this ``MetaData``, if
any.
:param tables:
Optional list of ``Table`` objects, which is a subset of the
total tables in the ``MetaData`` (others are ignored).
:param checkfirst:
Defaults to True, only issue DROPs for tables confirmed to be
present in the target database.
"""
if bind is None:
bind = _bind_or_error(self)
bind._run_visitor(ddl.SchemaDropper,
self,
checkfirst=checkfirst,
tables=tables)
class ThreadLocalMetaData(MetaData):
"""A MetaData variant that presents a different ``bind`` in every thread.
Makes the ``bind`` property of the MetaData a thread-local value, allowing
this collection of tables to be bound to different ``Engine``
implementations or connections in each thread.
The ThreadLocalMetaData starts off bound to None in each thread. Binds
must be made explicitly by assigning to the ``bind`` property or using
``connect()``. You can also re-bind dynamically multiple times per
thread, just like a regular ``MetaData``.
"""
__visit_name__ = 'metadata'
def __init__(self):
"""Construct a ThreadLocalMetaData."""
self.context = util.threading.local()
self.__engines = {}
super(ThreadLocalMetaData, self).__init__()
def bind(self):
"""The bound Engine or Connection for this thread.
This property may be assigned an Engine or Connection, or assigned a
string or URL to automatically create a basic Engine for this bind
with ``create_engine()``."""
return getattr(self.context, '_engine', None)
def _bind_to(self, bind):
"""Bind to a Connectable in the caller's thread."""
if isinstance(bind, (basestring, url.URL)):
try:
self.context._engine = self.__engines[bind]
except KeyError:
from sqlalchemy import create_engine
e = create_engine(bind)
self.__engines[bind] = e
self.context._engine = e
else:
# TODO: this is squirrely. we shouldnt have to hold onto engines
# in a case like this
if bind not in self.__engines:
self.__engines[bind] = bind
self.context._engine = bind
bind = property(bind, _bind_to)
def is_bound(self):
"""True if there is a bind for this thread."""
return (hasattr(self.context, '_engine') and
self.context._engine is not None)
def dispose(self):
"""Dispose all bound engines, in all thread contexts."""
for e in self.__engines.itervalues():
if hasattr(e, 'dispose'):
e.dispose()
class SchemaVisitor(visitors.ClauseVisitor):
"""Define the visiting for ``SchemaItem`` objects."""
__traverse_options__ = {'schema_visitor': True}
class _DDLCompiles(expression.ClauseElement):
def _compiler(self, dialect, **kw):
"""Return a compiler appropriate for this ClauseElement, given a
Dialect."""
return dialect.ddl_compiler(dialect, self, **kw)
class DDLElement(expression.Executable, _DDLCompiles):
"""Base class for DDL expression constructs.
This class is the base for the general purpose :class:`.DDL` class,
as well as the various create/drop clause constructs such as
:class:`.CreateTable`, :class:`.DropTable`, :class:`.AddConstraint`,
etc.
:class:`.DDLElement` integrates closely with SQLAlchemy events,
introduced in :ref:`event_toplevel`. An instance of one is
itself an event receiving callable::
event.listen(
users,
'after_create',
AddConstraint(constraint).execute_if(dialect='postgresql')
)
.. seealso::
:class:`.DDL`
:class:`.DDLEvents`
:ref:`event_toplevel`
:ref:`schema_ddl_sequences`
"""
_execution_options = expression.Executable.\
_execution_options.union({'autocommit': True})
target = None
on = None
dialect = None
callable_ = None
def execute(self, bind=None, target=None):
"""Execute this DDL immediately.
Executes the DDL statement in isolation using the supplied
:class:`.Connectable` or
:class:`.Connectable` assigned to the ``.bind``
property, if not supplied. If the DDL has a conditional ``on``
criteria, it will be invoked with None as the event.
:param bind:
Optional, an ``Engine`` or ``Connection``. If not supplied, a valid
:class:`.Connectable` must be present in the
``.bind`` property.
:param target:
Optional, defaults to None. The target SchemaItem for the
execute call. Will be passed to the ``on`` callable if any,
and may also provide string expansion data for the
statement. See ``execute_at`` for more information.
"""
if bind is None:
bind = _bind_or_error(self)
if self._should_execute(target, bind):
return bind.execute(self.against(target))
else:
bind.engine.logger.info(
"DDL execution skipped, criteria not met.")
@util.deprecated("0.7", "See :class:`.DDLEvents`, as well as "
":meth:`.DDLElement.execute_if`.")
def execute_at(self, event_name, target):
"""Link execution of this DDL to the DDL lifecycle of a SchemaItem.
Links this ``DDLElement`` to a ``Table`` or ``MetaData`` instance,
executing it when that schema item is created or dropped. The DDL
statement will be executed using the same Connection and transactional
context as the Table create/drop itself. The ``.bind`` property of
this statement is ignored.
:param event:
One of the events defined in the schema item's ``.ddl_events``;
e.g. 'before-create', 'after-create', 'before-drop' or 'after-drop'
:param target:
The Table or MetaData instance for which this DDLElement will
be associated with.
A DDLElement instance can be linked to any number of schema items.
``execute_at`` builds on the ``append_ddl_listener`` interface of
:class:`.MetaData` and :class:`.Table` objects.
Caveat: Creating or dropping a Table in isolation will also trigger
any DDL set to ``execute_at`` that Table's MetaData. This may change
in a future release.
"""
def call_event(target, connection, **kw):
if self._should_execute_deprecated(event_name,
target, connection, **kw):
return connection.execute(self.against(target))
event.listen(target, "" + event_name.replace('-', '_'), call_event)
@expression._generative
def against(self, target):
"""Return a copy of this DDL against a specific schema item."""
self.target = target
@expression._generative
def execute_if(self, dialect=None, callable_=None, state=None):
"""Return a callable that will execute this
DDLElement conditionally.
Used to provide a wrapper for event listening::
event.listen(
metadata,
'before_create',
DDL("my_ddl").execute_if(dialect='postgresql')
)
:param dialect: May be a string, tuple or a callable
predicate. If a string, it will be compared to the name of the
executing database dialect::
DDL('something').execute_if(dialect='postgresql')
If a tuple, specifies multiple dialect names::
DDL('something').execute_if(dialect=('postgresql', 'mysql'))
:param callable_: A callable, which will be invoked with
four positional arguments as well as optional keyword
arguments:
:ddl:
This DDL element.
:target:
The :class:`.Table` or :class:`.MetaData` object which is the
target of this event. May be None if the DDL is executed
explicitly.
:bind:
The :class:`.Connection` being used for DDL execution
:tables:
Optional keyword argument - a list of Table objects which are to
be created/ dropped within a MetaData.create_all() or drop_all()
method call.
:state:
Optional keyword argument - will be the ``state`` argument
passed to this function.
:checkfirst:
Keyword argument, will be True if the 'checkfirst' flag was
set during the call to ``create()``, ``create_all()``,
``drop()``, ``drop_all()``.
If the callable returns a true value, the DDL statement will be
executed.
:param state: any value which will be passed to the callable_
as the ``state`` keyword argument.
.. seealso::
:class:`.DDLEvents`
:ref:`event_toplevel`
"""
self.dialect = dialect
self.callable_ = callable_
self.state = state
def _should_execute(self, target, bind, **kw):
if self.on is not None and \
not self._should_execute_deprecated(None, target, bind, **kw):
return False
if isinstance(self.dialect, basestring):
if self.dialect != bind.engine.name:
return False
elif isinstance(self.dialect, (tuple, list, set)):
if bind.engine.name not in self.dialect:
return False
if self.callable_ is not None and \
not self.callable_(self, target, bind, state=self.state, **kw):
return False
return True
def _should_execute_deprecated(self, event, target, bind, **kw):
if self.on is None:
return True
elif isinstance(self.on, basestring):
return self.on == bind.engine.name
elif isinstance(self.on, (tuple, list, set)):
return bind.engine.name in self.on
else:
return self.on(self, event, target, bind, **kw)
def __call__(self, target, bind, **kw):
"""Execute the DDL as a ddl_listener."""
if self._should_execute(target, bind, **kw):
return bind.execute(self.against(target))
def _check_ddl_on(self, on):
if (on is not None and
(not isinstance(on, (basestring, tuple, list, set)) and
not util.callable(on))):
raise exc.ArgumentError(
"Expected the name of a database dialect, a tuple "
"of names, or a callable for "
"'on' criteria, got type '%s'." % type(on).__name__)
def bind(self):
if self._bind:
return self._bind
def _set_bind(self, bind):
self._bind = bind
bind = property(bind, _set_bind)
def _generate(self):
s = self.__class__.__new__(self.__class__)
s.__dict__ = self.__dict__.copy()
return s
class DDL(DDLElement):
"""A literal DDL statement.
Specifies literal SQL DDL to be executed by the database. DDL objects
function as DDL event listeners, and can be subscribed to those events
listed in :class:`.DDLEvents`, using either :class:`.Table` or
:class:`.MetaData` objects as targets. Basic templating support allows
a single DDL instance to handle repetitive tasks for multiple tables.
Examples::
from sqlalchemy import event, DDL
tbl = Table('users', metadata, Column('uid', Integer))
event.listen(tbl, 'before_create', DDL('DROP TRIGGER users_trigger'))
spow = DDL('ALTER TABLE %(table)s SET secretpowers TRUE')
event.listen(tbl, 'after_create', spow.execute_if(dialect='somedb'))
drop_spow = DDL('ALTER TABLE users SET secretpowers FALSE')
connection.execute(drop_spow)
When operating on Table events, the following ``statement``
string substitions are available::
%(table)s - the Table name, with any required quoting applied
%(schema)s - the schema name, with any required quoting applied
%(fullname)s - the Table name including schema, quoted if needed
The DDL's "context", if any, will be combined with the standard
substutions noted above. Keys present in the context will override
the standard substitutions.
"""
__visit_name__ = "ddl"
def __init__(self, statement, on=None, context=None, bind=None):
"""Create a DDL statement.
:param statement:
A string or unicode string to be executed. Statements will be
processed with Python's string formatting operator. See the
``context`` argument and the ``execute_at`` method.
A literal '%' in a statement must be escaped as '%%'.
SQL bind parameters are not available in DDL statements.
:param on:
Deprecated. See :meth:`.DDLElement.execute_if`.
Optional filtering criteria. May be a string, tuple or a callable
predicate. If a string, it will be compared to the name of the
executing database dialect::
DDL('something', on='postgresql')
If a tuple, specifies multiple dialect names::
DDL('something', on=('postgresql', 'mysql'))
If a callable, it will be invoked with four positional arguments
as well as optional keyword arguments:
:ddl:
This DDL element.
:event:
The name of the event that has triggered this DDL, such as
'after-create' Will be None if the DDL is executed explicitly.
:target:
The ``Table`` or ``MetaData`` object which is the target of
this event. May be None if the DDL is executed explicitly.
:connection:
The ``Connection`` being used for DDL execution
:tables:
Optional keyword argument - a list of Table objects which are to
be created/ dropped within a MetaData.create_all() or drop_all()
method call.
If the callable returns a true value, the DDL statement will be
executed.
:param context:
Optional dictionary, defaults to None. These values will be
available for use in string substitutions on the DDL statement.
:param bind:
Optional. A :class:`.Connectable`, used by
default when ``execute()`` is invoked without a bind argument.
.. seealso::
:class:`.DDLEvents`
:mod:`sqlalchemy.event`
"""
if not isinstance(statement, basestring):
raise exc.ArgumentError(
"Expected a string or unicode SQL statement, got '%r'" %
statement)
self.statement = statement
self.context = context or {}
self._check_ddl_on(on)
self.on = on
self._bind = bind
def __repr__(self):
return '<%s@%s; %s>' % (
type(self).__name__, id(self),
', '.join([repr(self.statement)] +
['%s=%r' % (key, getattr(self, key))
for key in ('on', 'context')
if getattr(self, key)]))
def _to_schema_column(element):
if hasattr(element, '__clause_element__'):
element = element.__clause_element__()
if not isinstance(element, Column):
raise exc.ArgumentError("schema.Column object expected")
return element
def _to_schema_column_or_string(element):
if hasattr(element, '__clause_element__'):
element = element.__clause_element__()
if not isinstance(element, (basestring, expression.ColumnElement)):
msg = "Element %r is not a string name or column element"
raise exc.ArgumentError(msg % element)
return element
class _CreateDropBase(DDLElement):
"""Base class for DDL constucts that represent CREATE and DROP or
equivalents.
The common theme of _CreateDropBase is a single
``element`` attribute which refers to the element
to be created or dropped.
"""
def __init__(self, element, on=None, bind=None):
self.element = element
self._check_ddl_on(on)
self.on = on
self.bind = bind
def _create_rule_disable(self, compiler):
"""Allow disable of _create_rule using a callable.
Pass to _create_rule using
util.portable_instancemethod(self._create_rule_disable)
to retain serializability.
"""
return False
class CreateSchema(_CreateDropBase):
"""Represent a CREATE SCHEMA statement.
.. versionadded:: 0.7.4
The argument here is the string name of the schema.
"""
__visit_name__ = "create_schema"
def __init__(self, name, quote=None, **kw):
"""Create a new :class:`.CreateSchema` construct."""
self.quote = quote
super(CreateSchema, self).__init__(name, **kw)
class DropSchema(_CreateDropBase):
"""Represent a DROP SCHEMA statement.
The argument here is the string name of the schema.
.. versionadded:: 0.7.4
"""
__visit_name__ = "drop_schema"
def __init__(self, name, quote=None, cascade=False, **kw):
"""Create a new :class:`.DropSchema` construct."""
self.quote = quote
self.cascade = cascade
super(DropSchema, self).__init__(name, **kw)
class CreateTable(_CreateDropBase):
"""Represent a CREATE TABLE statement."""
__visit_name__ = "create_table"
def __init__(self, element, on=None, bind=None):
"""Create a :class:`.CreateTable` construct.
:param element: a :class:`.Table` that's the subject
of the CREATE
:param on: See the description for 'on' in :class:`.DDL`.
:param bind: See the description for 'bind' in :class:`.DDL`.
"""
super(CreateTable, self).__init__(element, on=on, bind=bind)
self.columns = [CreateColumn(column)
for column in element.columns
]
class _DropView(_CreateDropBase):
"""Semi-public 'DROP VIEW' construct.
Used by the test suite for dialect-agnostic drops of views.
This object will eventually be part of a public "view" API.
"""
__visit_name__ = "drop_view"
class CreateColumn(_DDLCompiles):
"""Represent a :class:`.Column` as rendered in a CREATE TABLE statement,
via the :class:`.CreateTable` construct.
This is provided to support custom column DDL within the generation
of CREATE TABLE statements, by using the
compiler extension documented in :ref:`sqlalchemy.ext.compiler_toplevel`
to extend :class:`.CreateColumn`.
Typical integration is to examine the incoming :class:`.Column`
object, and to redirect compilation if a particular flag or condition
is found::
from sqlalchemy import schema
from sqlalchemy.ext.compiler import compiles
@compiles(schema.CreateColumn)
def compile(element, compiler, **kw):
column = element.element
if "special" not in column.info:
return compiler.visit_create_column(element, **kw)
text = "%s SPECIAL DIRECTIVE %s" % (
column.name,
compiler.type_compiler.process(column.type)
)
default = compiler.get_column_default_string(column)
if default is not None:
text += " DEFAULT " + default
if not column.nullable:
text += " NOT NULL"
if column.constraints:
text += " ".join(
compiler.process(const)
for const in column.constraints)
return text
The above construct can be applied to a :class:`.Table` as follows::
from sqlalchemy import Table, Metadata, Column, Integer, String
from sqlalchemy import schema
metadata = MetaData()
table = Table('mytable', MetaData(),
Column('x', Integer, info={"special":True}, primary_key=True),
Column('y', String(50)),
Column('z', String(20), info={"special":True})
)
metadata.create_all(conn)
Above, the directives we've added to the :attr:`.Column.info` collection
will be detected by our custom compilation scheme::
CREATE TABLE mytable (
x SPECIAL DIRECTIVE INTEGER NOT NULL,
y VARCHAR(50),
z SPECIAL DIRECTIVE VARCHAR(20),
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``.
This is essentially how to produce the same effect as using the
``system=True`` argument on :class:`.Column`, which marks a column
as an implicitly-present "system" column.
For example, suppose we wish to produce a :class:`.Table` which skips
rendering of the Postgresql ``xmin`` column against the Postgresql backend,
but on other backends does render it, in anticipation of a triggered rule.
A conditional compilation rule could skip this name only on Postgresql::
from sqlalchemy.schema import CreateColumn
@compiles(CreateColumn, "postgresql")
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, but only against the Postgresql backend.
.. 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.
"""
__visit_name__ = 'create_column'
def __init__(self, element):
self.element = element
class DropTable(_CreateDropBase):
"""Represent a DROP TABLE statement."""
__visit_name__ = "drop_table"
class CreateSequence(_CreateDropBase):
"""Represent a CREATE SEQUENCE statement."""
__visit_name__ = "create_sequence"
class DropSequence(_CreateDropBase):
"""Represent a DROP SEQUENCE statement."""
__visit_name__ = "drop_sequence"
class CreateIndex(_CreateDropBase):
"""Represent a CREATE INDEX statement."""
__visit_name__ = "create_index"
class DropIndex(_CreateDropBase):
"""Represent a DROP INDEX statement."""
__visit_name__ = "drop_index"
class AddConstraint(_CreateDropBase):
"""Represent an ALTER TABLE ADD CONSTRAINT statement."""
__visit_name__ = "add_constraint"
def __init__(self, element, *args, **kw):
super(AddConstraint, self).__init__(element, *args, **kw)
element._create_rule = util.portable_instancemethod(
self._create_rule_disable)
class DropConstraint(_CreateDropBase):
"""Represent an ALTER TABLE DROP CONSTRAINT statement."""
__visit_name__ = "drop_constraint"
def __init__(self, element, cascade=False, **kw):
self.cascade = cascade
super(DropConstraint, self).__init__(element, **kw)
element._create_rule = util.portable_instancemethod(
self._create_rule_disable)
def _bind_or_error(schemaitem, msg=None):
bind = schemaitem.bind
if not bind:
name = schemaitem.__class__.__name__
label = getattr(schemaitem, 'fullname',
getattr(schemaitem, 'name', None))
if label:
item = '%s %r' % (name, label)
else:
item = name
if isinstance(schemaitem, (MetaData, DDL)):
bindable = "the %s's .bind" % name
else:
bindable = "this %s's .metadata.bind" % name
if msg is None:
msg = "The %s is not bound to an Engine or Connection. "\
"Execution can not proceed without a database to execute "\
"against. Either execute with an explicit connection or "\
"assign %s to enable implicit execution." % \
(item, bindable)
raise exc.UnboundExecutionError(msg)
return bind
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