Merge 10.3 into 10.4

2 files changed, 16 insertions, 31 deletions

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 8fe1f34256c..dbe5ac15172 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -10214,9 +10214,12 @@ do_continue:;
     if (alter_info->requested_lock == Alter_info::ALTER_TABLE_LOCK_NONE)
       ha_alter_info.online= true;
     // Ask storage engine whether to use copy or in-place
-    ha_alter_info.inplace_supported=
-      table->file->check_if_supported_inplace_alter(&altered_table,
-                                                    &ha_alter_info);
+    {
+      Check_level_instant_set check_level_save(thd, CHECK_FIELD_WARN);
+      ha_alter_info.inplace_supported=
+        table->file->check_if_supported_inplace_alter(&altered_table,
+                                                      &ha_alter_info);
+    }
 
     if (alter_info->supports_algorithm(thd, &ha_alter_info) ||
         alter_info->supports_lock(thd, &ha_alter_info))
diff --git a/sql/transaction.cc b/sql/transaction.cc
index 135d274e6c6..e98672eaa9d 100644
--- a/sql/transaction.cc
+++ b/sql/transaction.cc
@@ -1,4 +1,5 @@
 /* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2009, 2021, 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
@@ -622,33 +623,6 @@ bool trans_rollback_to_savepoint(THD *thd, LEX_CSTRING name)
   if (thd->transaction.xid_state.check_has_uncommitted_xa())
     DBUG_RETURN(TRUE);
 
-  /**
-    Checking whether it is safe to release metadata locks acquired after
-    savepoint, if rollback to savepoint is successful.
-  
-    Whether it is safe to release MDL after rollback to savepoint depends
-    on storage engines participating in transaction:
-  
-    - InnoDB doesn't release any row-locks on rollback to savepoint so it
-      is probably a bad idea to release MDL as well.
-    - Binary log implementation in some cases (e.g when non-transactional
-      tables involved) may choose not to remove events added after savepoint
-      from transactional cache, but instead will write them to binary
-      log accompanied with ROLLBACK TO SAVEPOINT statement. Since the real
-      write happens at the end of transaction releasing MDL on tables
-      mentioned in these events (i.e. acquired after savepoint and before
-      rollback ot it) can break replication, as concurrent DROP TABLES
-      statements will be able to drop these tables before events will get
-      into binary log,
-  
-    For backward-compatibility reasons we always release MDL if binary
-    logging is off.
-  */
-  bool mdl_can_safely_rollback_to_savepoint=
-                (!((WSREP_EMULATE_BINLOG_NNULL(thd) || mysql_bin_log.is_open())
-                 && thd->variables.sql_log_bin) ||
-                 ha_rollback_to_savepoint_can_release_mdl(thd));
-
   if (ha_rollback_to_savepoint(thd, sv))
     res= TRUE;
   else if (((thd->variables.option_bits & OPTION_KEEP_LOG) ||
@@ -660,7 +634,15 @@ bool trans_rollback_to_savepoint(THD *thd, LEX_CSTRING name)
 
   thd->transaction.savepoints= sv;
 
-  if (!res && mdl_can_safely_rollback_to_savepoint)
+  if (res)
+    /* An error occurred during rollback; we cannot release any MDL */;
+  else if (thd->variables.sql_log_bin &&
+           (WSREP_EMULATE_BINLOG_NNULL(thd) || mysql_bin_log.is_open()))
+    /* In some cases (such as with non-transactional tables) we may
+    choose to preserve events that were added after the SAVEPOINT,
+    delimiting them by SAVEPOINT and ROLLBACK TO SAVEPOINT statements.
+    Prematurely releasing MDL on such objects would break replication. */;
+  else if (ha_rollback_to_savepoint_can_release_mdl(thd))
     thd->mdl_context.rollback_to_savepoint(sv->mdl_savepoint);
 
   DBUG_RETURN(MY_TEST(res));