[FTS][placeholder] Add doc length for fulltext index

src/objit/include/objit/common/ob_item_type.h

@@ -867,6 +867,7 @@ typedef enum ObItemType
   T_FUN_SYS_INNER_TABLE_OPTION_PRINTER = 1814,
   T_FUN_SYS_INNER_TABLE_SEQUENCE_GETTER = 1815,
   T_FUN_SYS_DECODE_TRACE_ID = 1816,
+  T_FUN_SYS_DOC_LENGTH = 1817,
   T_FUN_SYS_END = 2000,
   T_FUN_SYS_ALIGN_DATE4CMP = 2010,
   T_FUN_SYS_INNER_ROW_CMP_VALUE = 2011,

src/sql/engine/expr/ob_expr_eval_functions.cpp

@@ -1132,6 +1132,7 @@ static ObExpr::EvalFunc g_expr_eval_functions[] = {
   NULL, // ObExprWaitForExecutedGTIDSet::eval_wait_for_executed_gtid_set, /* 688 */
   NULL, // ObExprWaitUntilSQLThreadAfterGTIDs::eval_wait_until_sql_thread_after_gtids /* 689 */
   NULL, // ObExprLastRefreshScn::eval_last_refresh_scn                         /* 690 */
+  NULL, // ObExprDocLength::generate_doc_length,                      /*691*/
 };
 
 static ObExpr::EvalBatchFunc g_expr_eval_batch_functions[] = {