Add opsclass to exclusion constraint

Added new parameter :paramref:`_postgresql.ExcludeConstraint.ops` to the
:class:`_postgresql.ExcludeConstraint` object, to support operator class
specification with this constraint.  Pull request courtesy Alon Menczer.

Fixes: #5604
Closes: #5700
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5700
Pull-request-sha: f8613e100792fc0bb3cf300ec6aebc78ecdf0361

Change-Id: Iaf664131ec84f8c2fb05edf799198b8d3bb83597

2 files changed, 39 insertions, 9 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index d738393e7..66fe2526e 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -781,6 +781,8 @@ using the ``postgresql_where`` keyword argument::
 
   Index('my_index', my_table.c.id, postgresql_where=my_table.c.value > 10)
 
+.. _postgresql_operator_classes:
+
 Operator Classes
 ^^^^^^^^^^^^^^^^
 
@@ -797,11 +799,10 @@ The :class:`.Index` construct allows these to be specified via the
             'id': 'int4_ops'
         })
 
-Note that the keys in the ``postgresql_ops`` dictionary are the "key" name of
-the :class:`_schema.Column`, i.e. the name used to access it from the ``.c``
-collection of :class:`_schema.Table`,
-which can be configured to be different than
-the actual name of the column as expressed in the database.
+Note that the keys in the ``postgresql_ops`` dictionaries are the
+"key" name of the :class:`_schema.Column`, i.e. the name used to access it from
+the ``.c`` collection of :class:`_schema.Table`, which can be configured to be
+different than the actual name of the column as expressed in the database.
 
 If ``postgresql_ops`` is to be used against a complex SQL expression such
 as a function call, then to apply to the column it must be given a label
@@ -815,6 +816,14 @@ that is identified in the dictionary by name, e.g.::
             'id': 'int4_ops'
         })
 
+Operator classes are also supported by the
+:class:`_postgresql.ExcludeConstraint` construct using the
+:paramref:`_postgresql.ExcludeConstraint.ops` parameter. See that parameter for
+details.
+
+.. versionadded:: 1.3.20 added support for operator classes with
+   :class:`_postgresql.ExcludeConstraint`.
+
 
 Index Types
 ^^^^^^^^^^^
@@ -2417,9 +2426,13 @@ class PGDDLCompiler(compiler.DDLCompiler):
         elements = []
         for expr, name, op in constraint._render_exprs:
             kw["include_table"] = False
-            elements.append(
-                "%s WITH %s" % (self.sql_compiler.process(expr, **kw), op)
+            exclude_element = self.sql_compiler.process(expr, **kw) + (
+                (" " + constraint.ops[expr.key])
+                if hasattr(expr, "key") and expr.key in constraint.ops
+                else ""
             )
+
+            elements.append("%s WITH %s" % (exclude_element, op))
         text += "EXCLUDE USING %s (%s)" % (
             self.preparer.validate_sql_phrase(
                 constraint.using, IDX_USING
diff --git a/lib/sqlalchemy/dialects/postgresql/ext.py b/lib/sqlalchemy/dialects/postgresql/ext.py
index 78d9a96b6..4c8c3fc22 100644
--- a/lib/sqlalchemy/dialects/postgresql/ext.py
+++ b/lib/sqlalchemy/dialects/postgresql/ext.py
@@ -114,7 +114,8 @@ class ExcludeConstraint(ColumnCollectionConstraint):
             const = ExcludeConstraint(
                 (Column('period'), '&&'),
                 (Column('group'), '='),
-                where=(Column('group') != 'some group')
+                where=(Column('group') != 'some group'),
+                ops={'group': 'my_operator_class'}
             )
 
         The constraint is normally embedded into the :class:`_schema.Table`
@@ -133,7 +134,8 @@ class ExcludeConstraint(ColumnCollectionConstraint):
                     (some_table.c.period, '&&'),
                     (some_table.c.group, '='),
                     where=some_table.c.group != 'some group',
-                    name='some_table_excl_const'
+                    name='some_table_excl_const',
+                    ops={'group': 'my_operator_class'}
                 )
             )
 
@@ -171,6 +173,19 @@ class ExcludeConstraint(ColumnCollectionConstraint):
           If set, emit WHERE <predicate> when issuing DDL
           for this constraint.
 
+        :param ops:
+          Optional dictionary.  Used to define operator classes for the
+          elements; works the same way as that of the
+          :ref:`postgresql_ops <postgresql_operator_classes>`
+          parameter specified to the :class:`_schema.Index` construct.
+
+          .. versionadded:: 1.3.21
+
+          .. seealso::
+
+            :ref:`postgresql_operator_classes` - general description of how
+            PostgreSQL operator classes are specified.
+
         """
         columns = []
         render_exprs = []
@@ -209,6 +224,8 @@ class ExcludeConstraint(ColumnCollectionConstraint):
         if where is not None:
             self.where = coercions.expect(roles.StatementOptionRole, where)
 
+        self.ops = kw.get("ops", {})
+
     def _set_parent(self, table, **kw):
         super(ExcludeConstraint, self)._set_parent(table)