fix: ALTER COLUMN NOT NULL directive fails because of inappropriate syntax (googleapis#124)

* fix: ALTER COLUMN NOT NULL directive fails because of inappropriate syntax

* add alembic into nox session dependencies

* alembic dependency

Author: Ilya Gurov

google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py

@@ -15,10 +15,17 @@
 import pkg_resources
 import re
 
-from sqlalchemy import types, ForeignKeyConstraint
+from alembic.ddl.base import (
+    ColumnNullable,
+    ColumnType,
+    alter_column,
+    alter_table,
+    format_type,
+)
+from sqlalchemy import ForeignKeyConstraint, types, util
 from sqlalchemy.engine.base import Engine
 from sqlalchemy.engine.default import DefaultDialect
-from sqlalchemy import util
+from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.sql.compiler import (
     selectable,
     DDLCompiler,
@@ -27,6 +34,7 @@
     SQLCompiler,
     RESERVED_WORDS,
 )
+
 from google.cloud import spanner_dbapi
 from google.cloud.sqlalchemy_spanner._opentelemetry_tracing import trace_call
 
@@ -864,3 +872,28 @@ def do_execute_no_params(self, cursor, statement, context=None):
         }
         with trace_call("SpannerSqlAlchemy.ExecuteNoParams", trace_attributes):
             cursor.execute(statement)
+
+
+# Alembic ALTER operation override
+@compiles(ColumnNullable, "spanner")
+def visit_column_nullable(
+    element: "ColumnNullable", compiler: "SpannerDDLCompiler", **kw
+) -> str:
+    return "%s %s %s %s" % (
+        alter_table(compiler, element.table_name, element.schema),
+        alter_column(compiler, element.column_name),
+        format_type(compiler, element.existing_type),
+        "" if element.nullable else "NOT NULL",
+    )
+
+
+# Alembic ALTER operation override
+@compiles(ColumnType, "spanner")
+def visit_column_type(
+    element: "ColumnType", compiler: "SpannerDDLCompiler", **kw
+) -> str:
+    return "%s %s %s" % (
+        alter_table(compiler, element.table_name, element.schema),
+        alter_column(compiler, element.column_name),
+        "%s" % format_type(compiler, element.type_),
+    )

migration_test_cleanup.py

@@ -27,11 +27,11 @@
     config.read("setup.cfg")
 db_url = config.get("db", "default")
 
-project = re.findall(r'projects(.*?)instances', db_url)
-instance_id = re.findall(r'instances(.*?)databases', db_url)
+project = re.findall(r"projects(.*?)instances", db_url)
+instance_id = re.findall(r"instances(.*?)databases", db_url)
 
-client = spanner.Client(project="".join(project).replace('/', ''))
-instance = client.instance(instance_id="".join(instance_id).replace('/', ''))
+client = spanner.Client(project="".join(project).replace("/", ""))
+instance = client.instance(instance_id="".join(instance_id).replace("/", ""))
 database = instance.database("compliance-test")
 
 database.update_ddl(["DROP TABLE account", "DROP TABLE alembic_version"]).result(120)

noxfile.py

@@ -60,6 +60,12 @@ class = StreamHandler
         sa.Column('id', sa.Integer, primary_key=True),
         sa.Column('name', sa.String(50), nullable=False),
         sa.Column('description', sa.Unicode(200)),
+    )
+    op.alter_column(
+        'account',
+        'name',
+        existing_type=sa.String(50),
+        nullable=True,
     )"""
 
 

setup.py

@@ -19,7 +19,11 @@
 
 name = "sqlalchemy-spanner"
 description = "SQLAlchemy dialect integrated into Cloud Spanner database"
-dependencies = ["sqlalchemy>=1.1.13, <=1.3.23", "google-cloud-spanner>=3.3.0"]
+dependencies = [
+    "sqlalchemy>=1.1.13, <=1.3.23",
+    "google-cloud-spanner>=3.3.0",
+    "alembic",
+]
 extras = {
     "tracing": [
         "opentelemetry-api >= 1.1.0",