MDEV-25919 preparation: Remove trx_t::internal

With commit 1bd681c8 (MDEV-25506)
it no longer is necessary to run DDL and DML operations in
separate transactions. Let us remove the flag trx_t::internal.
Dictionary transactions will be distinguished by trx_t::dict_operation.

storage/innobase/dict/dict0stats.cc

@@ -542,10 +542,7 @@ dberr_t dict_stats_exec_sql(pars_info_t *pinfo, const char* sql, trx_t *trx)
     return que_eval_sql(pinfo, sql, FALSE, trx);
 
   trx= trx_create();
-  if (srv_read_only_mode)
-    trx_start_internal_read_only(trx);
-  else
-    trx_start_internal(trx);
+  trx_start_internal(trx);
 
   trx->dict_operation_lock_mode= RW_X_LATCH;
   dberr_t err= que_eval_sql(pinfo, sql, FALSE, trx);
@@ -2589,7 +2586,6 @@ dict_stats_save_index_stat(
 	char		db_utf8[MAX_DB_UTF8_LEN];
 	char		table_utf8[MAX_TABLE_UTF8_LEN];
 
-	ut_ad(!trx || trx->internal || trx->mysql_thd);
 	ut_d(dict_sys.assert_locked());
 
 	dict_fs2utf8(index->table->name.m_name, db_utf8, sizeof(db_utf8),
@@ -3247,11 +3243,7 @@ dict_stats_fetch_from_ps(
 
 	trx->isolation_level = TRX_ISO_READ_UNCOMMITTED;
 
-	if (srv_read_only_mode) {
-		trx_start_internal_read_only(trx);
-	} else {
-		trx_start_internal(trx);
-	}
+	trx_start_internal(trx);
 
 	dict_fs2utf8(table->name.m_name, db_utf8, sizeof(db_utf8),
 		     table_utf8, sizeof(table_utf8));

storage/innobase/fts/fts0fts.cc

@@ -2550,6 +2550,10 @@ fts_cmp_set_sync_doc_id(
 						to the one stored in CONFIG
 						table */
 {
+	if (srv_read_only_mode) {
+		return DB_READ_ONLY;
+	}
+
 	trx_t*		trx;
 	pars_info_t*	info;
 	dberr_t		error;
@@ -2566,11 +2570,7 @@ fts_cmp_set_sync_doc_id(
 	fts_table.table = table;
 
 	trx = trx_create();
-	if (srv_read_only_mode) {
-		trx_start_internal_read_only(trx);
-	} else {
-		trx_start_internal(trx);
-	}
+	trx_start_internal(trx);
 
 	trx->op_info = "update the next FTS document id";
 
@@ -5788,11 +5788,11 @@ fts_load_stopword(
 
 	if (!trx) {
 		trx = trx_create();
-		if (srv_read_only_mode) {
-			trx_start_internal_read_only(trx);
-		} else {
-			trx_start_internal(trx);
-		}
+#ifdef UNIV_DEBUG
+		trx->start_line = __LINE__;
+		trx->start_file = __FILE__;
+#endif
+		trx_start_internal_low(trx, !high_level_read_only);
 		trx->op_info = "upload FTS stopword";
 		new_trx = TRUE;
 	}

storage/innobase/handler/ha_innodb.cc

@@ -11363,8 +11363,9 @@ innobase_fts_load_stopword(
     mysql_mutex_unlock(&LOCK_global_system_variables);
   }
 
-  return fts_load_stopword(table, trx, stopword_table,
-                           THDVAR(thd, ft_enable_stopword), false);
+  return !high_level_read_only &&
+    fts_load_stopword(table, trx, stopword_table,
+                      THDVAR(thd, ft_enable_stopword), false);
 }
 
 /** Parse the table name into normal name and remote path if needed.
@@ -13387,7 +13388,6 @@ int ha_innobase::delete_table(const char *name)
     ut_ad(trx->will_lock);
     ut_ad(trx->state == TRX_STATE_ACTIVE);
     trx->dict_operation= true;
-    trx->internal= true;
   }
   else
   {

storage/innobase/include/trx0trx.h

@@ -95,18 +95,11 @@ trx_start_if_not_started_low(
 	trx_t*	trx,		/*!< in/out: transaction */
 	bool	read_write);	/*!< in: true if read write transaction */
 
-/*************************************************************//**
-Starts a transaction for internal processing. */
-void
-trx_start_internal_low(
-/*===================*/
-	trx_t*	trx);		/*!< in/out: transaction */
-
-/** Starts a read-only transaction for internal processing.
-@param[in,out] trx	transaction to be started */
-void
-trx_start_internal_read_only_low(
-	trx_t*	trx);
+/**
+Start a transaction for internal processing.
+@param trx          transaction
+@param read_write   whether writes may be performed */
+void trx_start_internal_low(trx_t *trx, bool read_write);
 
 #ifdef UNIV_DEBUG
 #define trx_start_if_not_started_xa(t, rw)			\
@@ -127,24 +120,13 @@ trx_start_internal_read_only_low(
 	do {							\
 	(t)->start_line = __LINE__;				\
 	(t)->start_file = __FILE__;				\
-	trx_start_internal_low((t));				\
-	} while (false)
-
-#define trx_start_internal_read_only(t)				\
-	do {							\
-	(t)->start_line = __LINE__;				\
-	(t)->start_file = __FILE__;				\
-	trx_start_internal_read_only_low(t);			\
+	trx_start_internal_low(t, true);			\
 	} while (false)
 #else
 #define trx_start_if_not_started(t, rw)				\
 	trx_start_if_not_started_low((t), rw)
 
-#define trx_start_internal(t)					\
-	trx_start_internal_low((t))
-
-#define trx_start_internal_read_only(t)				\
-	trx_start_internal_read_only_low(t)
+#define trx_start_internal(t) trx_start_internal_low(t, true)
 
 #define trx_start_if_not_started_xa(t, rw)			\
 	trx_start_if_not_started_xa_low((t), (rw))
@@ -848,12 +830,6 @@ struct trx_t : ilist_node<>
 					count of tables being flushed. */
 
 	/*------------------------------*/
-	bool		internal;	/*!< true if it is a system/internal
-					transaction background task. This
-					includes DDL transactions too.  Such
-					transactions are always treated as
-					read-write. */
-	/*------------------------------*/
 #ifdef UNIV_DEBUG
 	unsigned	start_line;	/*!< Track where it was started from */
 	const char*	start_file;	/*!< Filename where it was started */

storage/innobase/row/row0ins.cc

@@ -2635,7 +2635,7 @@ row_ins_clust_index_entry_low(
 	    && page_is_empty(block->frame)
 	    && !entry->is_metadata() && !trx->duplicates
 	    && !trx->check_unique_secondary && !trx->check_foreigns
-	    && !trx->dict_operation && !trx->internal
+	    && !trx->dict_operation
 	    && block->page.id().page_no() == index->page
 	    && !index->table->skip_alter_undo
 	    && !index->table->n_rec_locks

storage/innobase/trx/trx0purge.cc

@@ -280,8 +280,7 @@ trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr)
 		  && (srv_is_being_started
 		      || trx_rollback_is_active
 		      || srv_force_recovery >= SRV_FORCE_NO_BACKGROUND))
-	      || ((trx->mysql_thd || trx->internal)
-		  && srv_fast_shutdown));
+	      || srv_fast_shutdown);
 
 #ifdef	WITH_WSREP
 	if (wsrep_is_wsrep_xid(&trx->xid)) {

storage/innobase/trx/trx0trx.cc

@@ -131,8 +131,6 @@ trx_init(
 
 	trx->will_lock = false;
 
-	trx->internal = false;
-
 	trx->bulk_insert = false;
 
 	ut_d(trx->start_file = 0);
@@ -369,7 +367,6 @@ void trx_t::free()
   ut_ad(!n_mysql_tables_in_use);
   ut_ad(!mysql_log_file_name);
   ut_ad(!mysql_n_tables_locked);
-  ut_ad(!internal);
   ut_ad(!will_lock);
   ut_ad(error_state == DB_SUCCESS);
   ut_ad(magic_n == TRX_MAGIC_N);
@@ -440,7 +437,6 @@ void trx_t::free()
   MEM_NOACCESS(&fts_trx, sizeof fts_trx);
   MEM_NOACCESS(&fts_next_doc_id, sizeof fts_next_doc_id);
   MEM_NOACCESS(&flush_tables, sizeof flush_tables);
-  MEM_NOACCESS(&internal, sizeof internal);
 #ifdef UNIV_DEBUG
   MEM_NOACCESS(&start_line, sizeof start_line);
   MEM_NOACCESS(&start_file, sizeof start_file);
@@ -900,7 +896,7 @@ trx_start_low(
 	trx->auto_commit = thd_trx_is_auto_commit(trx->mysql_thd);
 
 	trx->read_only = srv_read_only_mode
-		|| (!trx->dict_operation && !trx->internal
+		|| (!trx->dict_operation
 		    && thd_trx_is_read_only(trx->mysql_thd));
 
 	if (!trx->auto_commit) {
@@ -2090,48 +2086,24 @@ trx_start_if_not_started_low(
 	ut_error;
 }
 
-/*************************************************************//**
-Starts a transaction for internal processing. */
-void
-trx_start_internal_low(
-/*===================*/
-	trx_t*	trx)		/*!< in/out: transaction */
-{
-	/* Ensure it is not flagged as an auto-commit-non-locking
-	transaction. */
-
-	trx->will_lock = true;
-
-	trx->internal = true;
-
-	trx_start_low(trx, true);
-}
-
-/** Starts a read-only transaction for internal processing.
-@param[in,out] trx	transaction to be started */
-void
-trx_start_internal_read_only_low(
-	trx_t*	trx)
+/**
+Start a transaction for internal processing.
+@param trx          transaction
+@param read_write   whether writes may be performed */
+void trx_start_internal_low(trx_t *trx, bool read_write)
 {
-	/* Ensure it is not flagged as an auto-commit-non-locking
-	transaction. */
-
-	trx->will_lock = true;
-
-	trx->internal = true;
-
-	trx_start_low(trx, false);
+  trx->will_lock= true;
+  trx_start_low(trx, read_write);
 }
 
 /** Start a transaction for a DDL operation.
 @param trx   transaction */
 void trx_start_for_ddl_low(trx_t *trx)
 {
-  ut_a(trx->state == TRX_STATE_NOT_STARTED);
   /* Flag this transaction as a dictionary operation, so that
   the data dictionary will be locked in crash recovery. */
   trx->dict_operation= true;
-  trx_start_internal_low(trx);
+  trx_start_internal_low(trx, true);
 }
 
 /*************************************************************//**