feat: optimize _index_query performance in OceanBase Oracle mode

oceanbase-sqlalchemy-plugin/oceanbase_sqlalchemy/cx_oracle.py

@@ -152,3 +152,62 @@ def _constraint_query(self, owner):
                 local.c.position,
             )
         )
+
+    @lru_cache()
+    def _index_query(self, owner):
+        """
+        Override _index_query to optimize performance in OceanBase Oracle mode.
+
+        Key optimization: Add filtering on all_ind_columns.table_name to reduce
+        the amount of data scanned early in the query execution.
+
+        Only for sqlalchemy 2.x compatibility.
+        """
+        return (
+            select(
+                dictionary.all_ind_columns.c.table_name,
+                dictionary.all_ind_columns.c.index_name,
+                dictionary.all_ind_columns.c.column_name,
+                dictionary.all_indexes.c.index_type,
+                dictionary.all_indexes.c.uniqueness,
+                dictionary.all_indexes.c.compression,
+                dictionary.all_indexes.c.prefix_length,
+                dictionary.all_ind_columns.c.descend,
+                dictionary.all_ind_expressions.c.column_expression,
+            )
+            .select_from(dictionary.all_ind_columns)
+            .join(
+                dictionary.all_indexes,
+                and_(
+                    dictionary.all_ind_columns.c.index_name
+                    == dictionary.all_indexes.c.index_name,
+                    dictionary.all_ind_columns.c.index_owner
+                    == dictionary.all_indexes.c.owner,
+                ),
+            )
+            .outerjoin(
+                dictionary.all_ind_expressions,
+                and_(
+                    dictionary.all_ind_expressions.c.index_name
+                    == dictionary.all_ind_columns.c.index_name,
+                    dictionary.all_ind_expressions.c.index_owner
+                    == dictionary.all_ind_columns.c.index_owner,
+                    dictionary.all_ind_expressions.c.column_position
+                    == dictionary.all_ind_columns.c.column_position,
+                ),
+            )
+            .where(
+                dictionary.all_indexes.c.table_owner == owner,
+                dictionary.all_indexes.c.table_name.in_(bindparam("all_objects")),
+                # Key optimization: add this condition to reduce all_ind_columns scan
+                dictionary.all_ind_columns.c.table_name.in_(bindparam("all_objects")),
+            )
+            .order_by(
+                dictionary.all_ind_columns.c.index_name,
+                dictionary.all_ind_columns.c.column_position,
+            )
+        )
+
+
+# Register dialect, similar to SQLAlchemy's cx_oracle.py
+dialect = OceanBaseDialect_cx_oracle