diff --git a/trytond/CHANGELOG b/trytond/CHANGELOG
index 81d4c403f6..06207f128f 100644
--- a/trytond/CHANGELOG
+++ b/trytond/CHANGELOG
@@ -1,3 +1,4 @@
+* Support subset operator between index definitions
 * Add sum_tree helper
 * Convert sum attribute into boolean
 * Store records selection on export
diff --git a/trytond/trytond/model/modelsql.py b/trytond/trytond/model/modelsql.py
index d9c5cf33b4..8edc9221b0 100644
--- a/trytond/trytond/model/modelsql.py
+++ b/trytond/trytond/model/modelsql.py
@@ -189,6 +189,26 @@ class Index:
             return str(value) if isinstance(value, Expression) else value
         return {k: _format(v) for k, v in self.options.items()}
 
+    def __lt__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplementedError
+        if (self.table != other.table
+                or self._options_cmp != other._options_cmp):
+            return False
+        if self == other:
+            return False
+        if len(self.expressions) >= len(other.expressions):
+            return False
+        for (c, u), (oc, ou) in zip(self.expressions, other.expressions):
+            if (str(c), u) != (str(oc), ou):
+                return False
+        return True
+
+    def __le__(self, other):
+        if not isinstance(other, self.__class__):
+            return NotImplementedError
+        return self < other or self == other
+
     class Unaccent(Expression):
         "Unaccent function if database support for index"
         __slots__ = ('_expression',)
diff --git a/trytond/trytond/tests/test_model_index.py b/trytond/trytond/tests/test_model_index.py
index 83ed5dfc7b..7c3ef89c37 100644
--- a/trytond/trytond/tests/test_model_index.py
+++ b/trytond/trytond/tests/test_model_index.py
@@ -129,6 +129,85 @@ class ModelIndexTestCase(unittest.TestCase):
 
         self.assertEqual(index1, index2)
 
+    def test_index_subset(self):
+        "Test Index subset"
+        table = Table('test')
+        index1 = Index(
+            table,
+            (table.foo, Index.Equality()))
+        index2 = Index(
+            table,
+            (table.foo, Index.Equality()),
+            (table.bar, Index.Equality()))
+
+        self.assertEqual(index1 < index2, True)
+        self.assertEqual(index2 < index1, False)
+
+    def test_index_subset_expressions(self):
+        "Test Index subset"
+        table = Table('test')
+        index1 = Index(
+            table,
+            (table.foo, Index.Equality()))
+        index2 = Index(
+            table,
+            (table.bar, Index.Equality()),
+            (table.foo, Index.Equality()))
+
+        self.assertEqual(index1 < index2, False)
+        self.assertEqual(index2 < index1, False)
+
+    def test_index_subset_same(self):
+        "Test Index subset"
+        table = Table('test')
+        index1 = Index(
+            table,
+            (table.foo, Index.Equality()))
+        index2 = Index(
+            table,
+            (table.foo, Index.Equality()))
+
+        self.assertEqual(index1 < index2, False)
+        self.assertEqual(index2 < index1, False)
+        self.assertLessEqual(index1, index2)
+
+    def test_index_subset_other(self):
+        "Test Index subset with other type"
+        table = Table('test')
+        index = Index(table)
+
+        self.assertEqual(index < 0, NotImplementedError)
+
+    def test_index_subset_table(self):
+        "Test Index subset on different table"
+        table1 = Table('foo')
+        table2 = Table('bar')
+        index1 = Index(
+            table1,
+            (table1.name, Index.Equality()))
+        index2 = Index(
+            table2,
+            (table2.name, Index.Equality()))
+
+        self.assertEqual(index1 < index2, False)
+        self.assertEqual(index2 < index1, False)
+
+    def test_index_subset_options(self):
+        "Test Index subset with different options"
+        table1 = Table('foo')
+        table2 = Table('bar')
+        index1 = Index(
+            table1,
+            (table1.name, Index.Equality()),
+            where=table1.name == 'bar')
+        index2 = Index(
+            table2,
+            (table2.name, Index.Equality()),
+            where=table2.name == 'foo')
+
+        self.assertEqual(index1 < index2, False)
+        self.assertEqual(index2 < index1, False)
+
     def test_index_hash(self):
         "Test Index hash"
         table1 = Table('test')