fix: Fix failed to execute _column_query (#46)

* fix: update OceanBase version handling in cx_oracle.py to prevent misidentification and ensure compatibility with NVARCHAR2 queries

* BugFix: Fixed decorator usage in cx_oracle.py for constraint data retrieval.

Author: yuanoOo

oceanbase-sqlalchemy-plugin/oceanbase_sqlalchemy/cx_oracle.py

@@ -60,17 +60,18 @@ def _get_server_version_info(self, connection):
         """
         Get OceanBase server version information
 
-        Issue: cx_Oceanbase driver returns "0.0.0.0.1" for connection.version,
+        Issue1: cx_Oceanbase driver returns "0.0.0.0.1" for connection.version,
         causing SQLAlchemy to misidentify it as Oracle 8 and set supports_unicode_binds to False,
         which encodes all string parameters as bytes, resulting in NVARCHAR2 query failures.
 
-        Solution: Extract the real OceanBase version number from v$version banner.
+        Issue2: Hard-code a pre-12c version so SQLAlchemy will not try to query
+        Oracle-only dictionary views such as ALL_TAB_IDENTITY_COLS, which
+        OceanBase does not implement. Unicode bind support is forced on in
+        initialize(), so we do not rely on the reported version for that.
+        _column_query() in base.py will fail with ORA-00942: table or view does not exist.
         """
 
-        # Fallback: Return a reasonable default version
-        # Note: Due to Python tuple comparison (4, x, x) < (9,) evaluates to True
-        # Use (21, 0, 0, 0, 0) to simulate Oracle 21g, ensuring it won't be misidentified as Oracle 8
-        return (21, 0, 0, 0, 0)
+        return (11, 2, 0, 0)
 
     def initialize(self, connection):
         """

oceanbase-sqlalchemy-plugin/setup.py

@@ -5,7 +5,7 @@
 
 setup(
     name="oceanbase-sqlalchemy",
-    version="0.5.1",
+    version="0.6.0",
     description="SQLAlchemy dialect for OceanBase Oracle mode (supports SQLAlchemy 1.3.x and 2.0+)",
     long_description=open("README.md", "r", encoding="utf-8").read(),
     long_description_content_type="text/markdown",