test: fix numeric compliance test

google/cloud/sqlalchemy_spanner/requirements.py

@@ -68,3 +68,9 @@ def get_isolation_levels(self, _):
             dict: isolation levels description.
         """
         return {"default": "SERIALIZABLE", "supported": ["SERIALIZABLE", "AUTOCOMMIT"]}
+
+    @property
+    def precision_numerics_enotation_large(self):
+        """target backend supports Decimal() objects using E notation
+        to represent very large values."""
+        return exclusions.open()

google/cloud/sqlalchemy_spanner/sqlalchemy_spanner.py

@@ -261,9 +261,6 @@ def visit_large_binary(self, type_, **kw):
     def visit_DECIMAL(self, type_, **kw):
         return "NUMERIC"
 
-    def visit_NUMERIC(self, type_, **kw):
-        return "NUMERIC"
-
     def visit_VARCHAR(self, type_, **kw):
         return "STRING({})".format(type_.length or "MAX")
 
@@ -276,6 +273,9 @@ def visit_BOOLEAN(self, type_, **kw):
     def visit_DATETIME(self, type_, **kw):
         return "TIMESTAMP"
 
+    def visit_NUMERIC(self, type_, **kw):
+        return "NUMERIC"
+
     def visit_BIGINT(self, type_, **kw):
         return "INT64"
 
@@ -302,6 +302,7 @@ class SpannerDialect(DefaultDialect):
     supports_sequences = True
     supports_native_enum = True
     supports_native_boolean = True
+    supports_native_decimal = True
 
     ddl_compiler = SpannerDDLCompiler
     preparer = SpannerIdentifierPreparer