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"""
This module defines standalone schema constraint classes.
"""
from sqlalchemy import schema
from migrate.exceptions import *
class ConstraintChangeset(object):
"""Base class for Constraint classes."""
def _normalize_columns(self, cols, table_name=False):
"""Given: column objects or names; return col names and
(maybe) a table"""
colnames = []
table = None
for col in cols:
if isinstance(col, schema.Column):
if col.table is not None and table is None:
table = col.table
if table_name:
col = '.'.join((col.table.name, col.name))
else:
col = col.name
colnames.append(col)
return colnames, table
def __do_imports(self, visitor_name, *a, **kw):
engine = kw.pop('engine', self.table.bind)
from migrate.changeset.databases.visitor import (get_engine_visitor,
run_single_visitor)
visitorcallable = get_engine_visitor(engine, visitor_name)
run_single_visitor(engine, visitorcallable, self, *a, **kw)
def create(self, *a, **kw):
"""Create the constraint in the database.
:param engine: the database engine to use. If this is \
:keyword:`None` the instance's engine will be used
:type engine: :class:`sqlalchemy.engine.base.Engine`
:param connection: reuse connection istead of creating new one.
:type connection: :class:`sqlalchemy.engine.base.Connection` instance
"""
# TODO: set the parent here instead of in __init__
self.__do_imports('constraintgenerator', *a, **kw)
def drop(self, *a, **kw):
"""Drop the constraint from the database.
:param engine: the database engine to use. If this is
:keyword:`None` the instance's engine will be used
:param cascade: Issue CASCADE drop if database supports it
:type engine: :class:`sqlalchemy.engine.base.Engine`
:type cascade: bool
:param connection: reuse connection istead of creating new one.
:type connection: :class:`sqlalchemy.engine.base.Connection` instance
:returns: Instance with cleared columns
"""
self.cascade = kw.pop('cascade', False)
self.__do_imports('constraintdropper', *a, **kw)
# the spirit of Constraint objects is that they
# are immutable (just like in a DB. they're only ADDed
# or DROPped).
#self.columns.clear()
return self
class PrimaryKeyConstraint(ConstraintChangeset, schema.PrimaryKeyConstraint):
"""Construct PrimaryKeyConstraint
Migrate's additional parameters:
:param cols: Columns in constraint.
:param table: If columns are passed as strings, this kw is required
:type table: Table instance
:type cols: strings or Column instances
"""
__migrate_visit_name__ = 'migrate_primary_key_constraint'
def __init__(self, *cols, **kwargs):
colnames, table = self._normalize_columns(cols)
table = kwargs.pop('table', table)
super(PrimaryKeyConstraint, self).__init__(*colnames, **kwargs)
if table is not None:
self._set_parent(table)
def autoname(self):
"""Mimic the database's automatic constraint names"""
return "%s_pkey" % self.table.name
class ForeignKeyConstraint(ConstraintChangeset, schema.ForeignKeyConstraint):
"""Construct ForeignKeyConstraint
Migrate's additional parameters:
:param columns: Columns in constraint
:param refcolumns: Columns that this FK reffers to in another table.
:param table: If columns are passed as strings, this kw is required
:type table: Table instance
:type columns: list of strings or Column instances
:type refcolumns: list of strings or Column instances
"""
__migrate_visit_name__ = 'migrate_foreign_key_constraint'
def __init__(self, columns, refcolumns, *args, **kwargs):
colnames, table = self._normalize_columns(columns)
table = kwargs.pop('table', table)
refcolnames, reftable = self._normalize_columns(refcolumns,
table_name=True)
super(ForeignKeyConstraint, self).__init__(colnames, refcolnames, *args,
**kwargs)
if table is not None:
self._set_parent(table)
@property
def referenced(self):
return [e.column for e in self.elements]
@property
def reftable(self):
return self.referenced[0].table
def autoname(self):
"""Mimic the database's automatic constraint names"""
if hasattr(self.columns, 'keys'):
# SA <= 0.5
firstcol = self.columns[self.columns.keys()[0]]
ret = "%(table)s_%(firstcolumn)s_fkey" % dict(
table=firstcol.table.name,
firstcolumn=firstcol.name,)
else:
# SA >= 0.6
ret = "%(table)s_%(firstcolumn)s_fkey" % dict(
table=self.table.name,
firstcolumn=self.columns[0],)
return ret
class CheckConstraint(ConstraintChangeset, schema.CheckConstraint):
"""Construct CheckConstraint
Migrate's additional parameters:
:param sqltext: Plain SQL text to check condition
:param columns: If not name is applied, you must supply this kw\
to autoname constraint
:param table: If columns are passed as strings, this kw is required
:type table: Table instance
:type columns: list of Columns instances
:type sqltext: string
"""
__migrate_visit_name__ = 'migrate_check_constraint'
def __init__(self, sqltext, *args, **kwargs):
cols = kwargs.pop('columns', [])
if not cols and not kwargs.get('name', False):
raise InvalidConstraintError('You must either set "name"'
'parameter or "columns" to autogenarate it.')
colnames, table = self._normalize_columns(cols)
table = kwargs.pop('table', table)
schema.CheckConstraint.__init__(self, sqltext, *args, **kwargs)
if table is not None:
self._set_parent(table)
self.colnames = colnames
def autoname(self):
return "%(table)s_%(cols)s_check" % \
dict(table=self.table.name, cols="_".join(self.colnames))
class UniqueConstraint(ConstraintChangeset, schema.UniqueConstraint):
"""Construct UniqueConstraint
Migrate's additional parameters:
:param cols: Columns in constraint.
:param table: If columns are passed as strings, this kw is required
:type table: Table instance
:type cols: strings or Column instances
.. versionadded:: 0.6.0
"""
__migrate_visit_name__ = 'migrate_unique_constraint'
def __init__(self, *cols, **kwargs):
self.colnames, table = self._normalize_columns(cols)
table = kwargs.pop('table', table)
super(UniqueConstraint, self).__init__(*self.colnames, **kwargs)
if table is not None:
self._set_parent(table)
def autoname(self):
"""Mimic the database's automatic constraint names"""
return "%s_%s_key" % (self.table.name, self.colnames[0])
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