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, 10 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/provision.py b/lib/sqlalchemy/testing/provision.py
index a8650f222..43821854c 100644
--- a/lib/sqlalchemy/testing/provision.py
+++ b/lib/sqlalchemy/testing/provision.py
@@ -475,3 +475,13 @@ def upsert(cfg, table, returning, set_lambda=None):
     raise NotImplementedError(
         f"backend does not include an upsert implementation: {cfg.db.url}"
     )
+
+
+@register.init
+def normalize_sequence(cfg, sequence):
+    """Normalize sequence parameters for dialect that don't start with 1
+    by default.
+
+    The default implementation does nothing
+    """
+    return sequence