fix: don't introspect internal UNIQUE constraints (#244)

Author: IlyaFaer

create_test_database.py

@@ -70,7 +70,7 @@ def create_test_instance():
     configs = list(CLIENT.list_instance_configs())
     if not USE_EMULATOR:
         # Filter out non "us" locations
-        configs = [config for config in configs if "-us-" in config.name]
+        configs = [config for config in configs if "europe-north1" in config.name]
 
     instance_config = configs[0].name
     create_time = str(int(time.time()))

google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py

@@ -873,7 +873,12 @@ def get_unique_constraints(self, connection, table_name, schema=None, **kw):
 FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc
 JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS ccu
     ON ccu.CONSTRAINT_NAME = tc.CONSTRAINT_NAME
-WHERE tc.TABLE_NAME="{table_name}" AND tc.CONSTRAINT_TYPE = "UNIQUE"
+LEFT JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS rc
+    on tc.CONSTRAINT_NAME = rc.CONSTRAINT_NAME
+WHERE
+    tc.TABLE_NAME="{table_name}"
+    AND tc.CONSTRAINT_TYPE = "UNIQUE"
+    AND rc.CONSTRAINT_NAME IS NOT NULL
 """.format(
             table_name=table_name
         )