def to_constraint(self, migration_context=None):
if not util.sqla_100:
raise NotImplementedError(
"ExcludeConstraint not supported until SQLAlchemy 1.0")
if self._orig_constraint is not None:
return self._orig_constraint
schema_obj = schemaobj.SchemaObjects(migration_context)
t = schema_obj.table(self.table_name, schema=self.schema)
excl = ExcludeConstraint(
*self.elements,
name=self.constraint_name,
where=self.where,
**self.kw
)
for expr, name, oper in excl._render_exprs:
t.append_column(Column(name, NULLTYPE))
t.append_constraint(excl)
return excl
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