Add support for identity columns

Added the :class:`_schema.Identity` construct that can be used to
configure identity columns rendered with GENERATED { ALWAYS |
BY DEFAULT } AS IDENTITY. Currently the supported backends are
PostgreSQL >= 10, Oracle >= 12 and MSSQL (with different syntax
and a subset of functionalities).

Fixes: #5362
Fixes: #5324
Fixes: #5360

Change-Id: Iecea6f3ceb36821e8b96f0b61049b580507a1875

1 files changed, 15 insertions, 0 deletions

diff --git a/test/dialect/postgresql/test_compiler.py b/test/dialect/postgresql/test_compiler.py
index ce285007f..aa355549b 100644
--- a/test/dialect/postgresql/test_compiler.py
+++ b/test/dialect/postgresql/test_compiler.py
@@ -8,6 +8,7 @@ from sqlalchemy import delete
 from sqlalchemy import Enum
 from sqlalchemy import exc
 from sqlalchemy import func
+from sqlalchemy import Identity
 from sqlalchemy import Index
 from sqlalchemy import Integer
 from sqlalchemy import MetaData
@@ -1689,6 +1690,20 @@ class CompileTest(fixtures.TestBase, AssertsCompiledSQL):
             dialect=postgresql.dialect(),
         )
 
+    def test_column_identity(self):
+        # all other tests are in test_identity_column.py
+        m = MetaData()
+        t = Table(
+            "t",
+            m,
+            Column("y", Integer, Identity(always=True, start=4, increment=7)),
+        )
+        self.assert_compile(
+            schema.CreateTable(t),
+            "CREATE TABLE t (y INTEGER GENERATED ALWAYS AS IDENTITY "
+            "(INCREMENT BY 7 START WITH 4))",
+        )
+
 
 class InsertOnConflictTest(fixtures.TestBase, AssertsCompiledSQL):
     __dialect__ = postgresql.dialect()