Follow-up fixes for MDEV-10139 Support for InnoDB SEQUENCE objects

Because SEQUENCE objects or NO_ROLLBACK tables do not support locking
or MVCC or transactions, avoid starting a transaction.

row_upd_step(): Do not start a transaction. Let the caller do that.

que_thr_step(): Call trx_start_if_not_started_xa() for QUE_NODE_UPDATE.
(The InnoDB SQL parser is not used for accessing NO_ROLLBACK tables.)

row_ins_step(): Correct a too strict assertion and comment about
concurrency. Multiple concurrent readers are allowed.

row_update_for_mysql_using_upd_graph(): Do not start the transaction
for NO_ROLLBACK tables.

row_search_mvcc(): For NO_ROLLBACK tables, skip locking even inside
LOCK TABLES. Only call trx_start_if_not_started() at the start
of a statement, not for each individual request.

storage/innobase/que/que0que.cc

@@ -1031,6 +1031,7 @@ que_thr_step(
 	} else if (type == QUE_NODE_INSERT) {
 		thr = row_ins_step(thr);
 	} else if (type == QUE_NODE_UPDATE) {
+		trx_start_if_not_started_xa(thr_get_trx(thr), true);
 		thr = row_upd_step(thr);
 	} else if (type == QUE_NODE_FETCH) {
 		thr = fetch_step(thr);

storage/innobase/row/row0ins.cc

@@ -3726,10 +3726,10 @@ row_ins_step(
 	it again here. But we must write trx->id to node->trx_id_buf. */
 
 	if (node->table->no_rollback()) {
-		/* No-rollback tables should only be accessed by a
-		single thread at a time. Concurrency control (mutual
-		exclusion) must be guaranteed by the SQL layer. */
-		DBUG_ASSERT(node->table->n_ref_count == 1);
+		/* No-rollback tables should only be written to by a
+		single thread at a time, but there can be multiple
+		concurrent readers. We must hold an open table handle. */
+		DBUG_ASSERT(node->table->n_ref_count > 0);
 		DBUG_ASSERT(node->ins_type == INS_DIRECT);
 		/* No-rollback tables can consist only of a single index. */
 		DBUG_ASSERT(UT_LIST_GET_LEN(node->entry_list) == 1);

storage/innobase/row/row0mysql.cc

@@ -1888,7 +1888,9 @@ row_update_for_mysql_using_upd_graph(
 
 	init_fts_doc_id_for_ref(table, &fk_depth);
 
+	if (!table->no_rollback()) {
 		trx_start_if_not_started_xa(trx, true);
+	}
 
 	if (dict_table_is_referenced_by_foreign_key(table)) {
 		/* Share lock the data dictionary to prevent any

storage/innobase/row/row0sel.cc

@@ -4481,8 +4481,6 @@ row_search_mvcc(
 	      || MVCC::is_view_active(trx->read_view)
 	      || srv_read_only_mode);
 
-	trx_start_if_not_started(trx, false);
-
 	if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
 	    && prebuilt->select_lock_type != LOCK_NONE
 	    && trx->mysql_thd != NULL
@@ -4533,9 +4531,14 @@ row_search_mvcc(
 			fputc('\n', stderr);
 			ut_error;
 		}
+	} else if (prebuilt->table->no_rollback()) {
+		/* NO_ROLLBACK tables do not support MVCC or locking. */
+		prebuilt->select_lock_type = LOCK_NONE;
+		prebuilt->sql_stat_start = FALSE;
 	} else if (prebuilt->select_lock_type == LOCK_NONE) {
 		/* This is a consistent read */
 		/* Assign a read view for the query */
+		trx_start_if_not_started(trx, false);
 
 		if (!srv_read_only_mode) {
 			trx_assign_read_view(trx);
@@ -4543,6 +4546,7 @@ row_search_mvcc(
 
 		prebuilt->sql_stat_start = FALSE;
 	} else {
+		trx_start_if_not_started(trx, false);
 wait_table_again:
 		err = lock_table(0, prebuilt->table,
 				 prebuilt->select_lock_type == LOCK_S

storage/innobase/row/row0upd.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2016, MariaDB Corporation.
+Copyright (c) 2015, 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -3128,7 +3128,8 @@ row_upd_clust_step(
 		}
 	}
 
-	ut_ad(lock_trx_has_rec_x_lock(thr_get_trx(thr), index->table,
+	ut_ad(index->table->no_rollback()
+	      || lock_trx_has_rec_x_lock(thr_get_trx(thr), index->table,
 					 btr_pcur_get_block(pcur),
 					 page_rec_get_heap_no(rec)));
 
@@ -3330,8 +3331,6 @@ row_upd_step(
 
 	trx = thr_get_trx(thr);
 
-	trx_start_if_not_started_xa(trx, true);
-
 	node = static_cast<upd_node_t*>(thr->run_node);
 
 	sel_node = node->select;