Revert automatic set of sequence start to 1

The :class:`.Sequence` construct restores itself to the DDL behavior it
had prior to the 1.4 series, where creating a :class:`.Sequence` with
no additional arguments will emit a simple ``CREATE SEQUENCE`` instruction
**without** any additional parameters for "start value".   For most backends,
this is how things worked previously in any case; **however**, for
MS SQL Server, the default value on this database is
``-2**63``; to prevent this generally impractical default
from taking effect on SQL Server, the :paramref:`.Sequence.start` parameter
should be provided.   As usage of :class:`.Sequence` is unusual
for SQL Server which for many years has standardized on ``IDENTITY``,
it is hoped that this change has minimal impact.

Fixes: #7211
Change-Id: I1207ea10c8cb1528a1519a0fb3581d9621c27b31

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index f3db1a95e..5eab8f47c 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -27,9 +27,13 @@ default corresponding to the column.
 To specify a specific named sequence to be used for primary key generation,
 use the :func:`~sqlalchemy.schema.Sequence` construct::
 
-    Table('sometable', metadata,
-            Column('id', Integer, Sequence('some_id_seq'), primary_key=True)
+    Table(
+        "sometable",
+        metadata,
+        Column(
+            "id", Integer, Sequence("some_id_seq", start=1), primary_key=True
         )
+    )
 
 When SQLAlchemy issues a single INSERT statement, to fulfill the contract of
 having the "last insert identifier" available, a RETURNING clause is added to