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