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# Copyright (C) 2013-2015 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
from ...sql.schema import ColumnCollectionConstraint
from ...sql import expression
from ... import util
class ExcludeConstraint(ColumnCollectionConstraint):
"""A table-level EXCLUDE constraint.
Defines an EXCLUDE constraint as described in the `postgres
documentation`__.
__ http://www.postgresql.org/docs/9.0/\
static/sql-createtable.html#SQL-CREATETABLE-EXCLUDE
"""
__visit_name__ = 'exclude_constraint'
where = None
def __init__(self, *elements, **kw):
"""
:param \*elements:
A sequence of two tuples of the form ``(column, operator)`` where
column must be a column name or Column object and operator must
be a string containing the operator to use.
: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 using:
Optional string. If set, emit USING <index_method> when issuing DDL
for this constraint. Defaults to 'gist'.
:param where:
Optional string. If set, emit WHERE <predicate> when issuing DDL
for this constraint.
"""
columns = []
render_exprs = []
self.operators = {}
expressions, operators = zip(*elements)
for (expr, column, strname, add_element), operator in zip(
self._extract_col_expression_collection(expressions),
operators
):
if add_element is not None:
columns.append(add_element)
name = column.name if column is not None else strname
if name is not None:
# backwards compat
self.operators[name] = operator
expr = expression._literal_as_text(expr)
render_exprs.append(
(expr, name, operator)
)
self._render_exprs = render_exprs
ColumnCollectionConstraint.__init__(
self,
*columns,
name=kw.get('name'),
deferrable=kw.get('deferrable'),
initially=kw.get('initially')
)
self.using = kw.get('using', 'gist')
where = kw.get('where')
if where:
self.where = expression._literal_as_text(where)
def copy(self, **kw):
elements = [(col, self.operators[col])
for col in self.columns.keys()]
c = self.__class__(*elements,
name=self.name,
deferrable=self.deferrable,
initially=self.initially)
c.dispatch._update(self.dispatch)
return c
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