Implement EXCLUDE constraints for postgres.

1 files changed, 73 insertions, 0 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/constraints.py b/lib/sqlalchemy/dialects/postgresql/constraints.py
new file mode 100644
index 000000000..88d688a05
--- /dev/null
+++ b/lib/sqlalchemy/dialects/postgresql/constraints.py
@@ -0,0 +1,73 @@
+# Copyright (C) 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
+from sqlalchemy.schema import ColumnCollectionConstraint
+from sqlalchemy.sql import expression
+
+class ExcludeConstraint(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__ = '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.
+
+        """
+        ColumnCollectionConstraint.__init__(
+            self,
+            *[col for col, op in elements],
+            name=kw.get('name'),
+            deferrable=kw.get('deferrable'),
+            initially=kw.get('initially')
+            )
+        self.operators = {}
+        for col_or_string, op in elements:
+            name = getattr(col_or_string, 'name', col_or_string)
+            self.operators[name] = op
+        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
+