diff --git a/VERSION b/VERSION
index c986c33613e..9d94c079411 100644
--- a/VERSION
+++ b/VERSION
@@ -1,4 +1,4 @@
 MYSQL_VERSION_MAJOR=10
 MYSQL_VERSION_MINOR=5
-MYSQL_VERSION_PATCH=14
+MYSQL_VERSION_PATCH=15
 SERVER_MATURITY=stable
diff --git a/include/my_alarm.h b/include/my_alarm.h
index 14a81c1ef17..df5cb7f51de 100644
--- a/include/my_alarm.h
+++ b/include/my_alarm.h
@@ -31,7 +31,7 @@ extern ulong my_time_to_wait_for_lock;
 #include <signal.h>
 #ifdef HAVE_SIGHANDLER_T
 #define sig_return sighandler_t
-#elif defined(SOLARIS) || defined(__sun) || defined(__APPLE__) || defined(__FreeBSD__)
+#elif defined(SOLARIS) || defined(__sun) || defined(__APPLE__) || defined(__FreeBSD__) || defined(_AIX)
 typedef void (*sig_return)(int); /* Returns type from signal */
 #else
 typedef void (*sig_return)(void); /* Returns type from signal */
diff --git a/mysql-test/main/backup_locks.result b/mysql-test/main/backup_locks.result
index 1505c39f166..1e567c1a58d 100644
--- a/mysql-test/main/backup_locks.result
+++ b/mysql-test/main/backup_locks.result
@@ -39,6 +39,28 @@ MDL_INTENTION_EXCLUSIVE	Schema metadata lock	test
 select * from t1;
 ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
 backup unlock;
+connection con1;
+connection default;
+#
+# Check that BACKUP LOCK blocks some operations
+#
+create sequence seq1;
+create sequence seq2;
+backup lock seq1;
+connection con1;
+CREATE OR REPLACE SEQUENCE seq1 START -28;
+ERROR HY000: Sequence 'test.seq1' values are conflicting
+SET STATEMENT max_statement_time=10 FOR CREATE OR REPLACE SEQUENCE seq1 START 50;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+SET STATEMENT max_statement_time=10 FOR ALTER SEQUENCE IF EXISTS seq1 NOMAXVALUE;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+SET STATEMENT max_statement_time=10 FOR ALTER SEQUENCE IF EXISTS seq1 MAXVALUE 1000;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+SET STATEMENT max_statement_time=10 for rename table seq2 to seq3, seq3 to seq1;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+connection default;
+backup unlock;
+drop table seq1,seq2;
 #
 # BACKUP LOCK and BACKUP UNLOCK are not allowed in procedures.
 #
@@ -141,7 +163,6 @@ ERROR HY000: Can't execute the given command because you have active locked tabl
 SET STATEMENT max_statement_time=180 FOR BACKUP LOCK test.u;
 # restart
 #
-connection con1;
 connection default;
 disconnect con1;
 show tables;
diff --git a/mysql-test/main/backup_locks.test b/mysql-test/main/backup_locks.test
index d2f3d95d703..1271abfd993 100644
--- a/mysql-test/main/backup_locks.test
+++ b/mysql-test/main/backup_locks.test
@@ -43,10 +43,39 @@ SELECT LOCK_MODE, LOCK_TYPE, TABLE_SCHEMA, TABLE_NAME FROM information_schema.me
 --error ER_LOCK_DEADLOCK
 select * from t1;
 backup unlock;
+connection con1;
+--reap
+connection default;
+
+--echo #
+--echo # Check that BACKUP LOCK blocks some operations
+--echo #
+
+# These test has to be done with timeouts as we want to ensure that the tables
+# doesn't change
+
+create sequence seq1;
+create sequence seq2;
+backup lock seq1;
+connection con1;
+--error ER_SEQUENCE_INVALID_DATA
+CREATE OR REPLACE SEQUENCE seq1 START -28;
+--error ER_STATEMENT_TIMEOUT
+SET STATEMENT max_statement_time=10 FOR CREATE OR REPLACE SEQUENCE seq1 START 50;
+--error ER_STATEMENT_TIMEOUT
+SET STATEMENT max_statement_time=10 FOR ALTER SEQUENCE IF EXISTS seq1 NOMAXVALUE;
+--error ER_STATEMENT_TIMEOUT
+SET STATEMENT max_statement_time=10 FOR ALTER SEQUENCE IF EXISTS seq1 MAXVALUE 1000;
+--error ER_STATEMENT_TIMEOUT
+SET STATEMENT max_statement_time=10 for rename table seq2 to seq3, seq3 to seq1;
+connection default;
+backup unlock;
+drop table seq1,seq2;
 
 --echo #
 --echo # BACKUP LOCK and BACKUP UNLOCK are not allowed in procedures.
 --echo #
+
 delimiter |;
 --error ER_SP_BADSTATEMENT
 CREATE PROCEDURE p_BACKUP_LOCK()
@@ -162,8 +191,6 @@ SET STATEMENT max_statement_time=180 FOR BACKUP LOCK test.u;
 
 --echo #
 
-connection con1;
---reap
 connection default;
 disconnect con1;
 show tables;
diff --git a/mysql-test/main/group_min_max.result b/mysql-test/main/group_min_max.result
index b316d28422e..4bdacd5e4a1 100644
--- a/mysql-test/main/group_min_max.result
+++ b/mysql-test/main/group_min_max.result
@@ -4027,3 +4027,40 @@ drop table t1;
 #
 # End of 10.1 tests
 #
+#
+# MDEV-27442 Wrong result upon query with DISTINCT and EXISTS subquery
+#
+CREATE TABLE t1 (a int, b int, KEY b (b,a)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (0,100),(2,100),(2,101),(3,102);
+# Must not use Using index for group-by
+explain SELECT DISTINCT b FROM t1 WHERE EXISTS ( SELECT 1 FROM DUAL WHERE a > 1 );
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	b	10	NULL	4	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+SELECT DISTINCT b FROM t1 WHERE EXISTS ( SELECT 1 FROM DUAL WHERE a > 1 );
+b
+100
+101
+102
+DROP TABLE t1;
+#
+# MDEV-26585 Wrong query results when `using index for group-by`
+#
+CREATE TABLE `t1` (
+`id` int(11) NOT NULL AUTO_INCREMENT,
+`owner_id` int(11) DEFAULT NULL,
+`foo` tinyint(1) DEFAULT 0,
+`whatever` varchar(255) DEFAULT NULL,
+PRIMARY KEY (`id`),
+KEY `index_t1_on_owner_id_and_foo` (`owner_id`,`foo`)
+) engine=InnoDB DEFAULT CHARSET=utf8;
+INSERT INTO t1 (owner_id, foo, whatever)
+VALUES (1, TRUE, "yello"), (1, FALSE, "yello"), (2, TRUE, "yello"),
+(2, TRUE, "yello"), (2, FALSE, "yello");
+EXPLAIN SELECT DISTINCT owner_id FROM t1 WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	index_t1_on_owner_id_and_foo	7	NULL	5	Using where; Using index
+SELECT DISTINCT owner_id FROM t1 WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);
+owner_id
+1
+DROP TABLE t1;
diff --git a/mysql-test/main/group_min_max.test b/mysql-test/main/group_min_max.test
index 526552dda92..b1d912684c6 100644
--- a/mysql-test/main/group_min_max.test
+++ b/mysql-test/main/group_min_max.test
@@ -4,7 +4,7 @@
 #
 
 --source include/default_optimizer_switch.inc
-
+--source include/have_innodb.inc
 #
 # TODO:
 # Add queries with:
@@ -1689,3 +1689,34 @@ drop table t1;
 --echo #
 --echo # End of 10.1 tests
 --echo #
+
+--echo #
+--echo # MDEV-27442 Wrong result upon query with DISTINCT and EXISTS subquery
+--echo #
+
+CREATE TABLE t1 (a int, b int, KEY b (b,a)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (0,100),(2,100),(2,101),(3,102);
+--echo # Must not use Using index for group-by
+explain SELECT DISTINCT b FROM t1 WHERE EXISTS ( SELECT 1 FROM DUAL WHERE a > 1 );
+SELECT DISTINCT b FROM t1 WHERE EXISTS ( SELECT 1 FROM DUAL WHERE a > 1 );
+DROP TABLE t1;
+
+--echo #
+--echo # MDEV-26585 Wrong query results when `using index for group-by`
+--echo #
+
+CREATE TABLE `t1` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `owner_id` int(11) DEFAULT NULL,
+  `foo` tinyint(1) DEFAULT 0,
+  `whatever` varchar(255) DEFAULT NULL,
+  PRIMARY KEY (`id`),
+  KEY `index_t1_on_owner_id_and_foo` (`owner_id`,`foo`)
+) engine=InnoDB DEFAULT CHARSET=utf8;
+
+INSERT INTO t1 (owner_id, foo, whatever)
+VALUES (1, TRUE, "yello"), (1, FALSE, "yello"), (2, TRUE, "yello"),
+       (2, TRUE, "yello"), (2, FALSE, "yello");
+EXPLAIN SELECT DISTINCT owner_id FROM t1 WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);
+SELECT DISTINCT owner_id FROM t1 WHERE foo = true GROUP BY owner_id HAVING (COUNT(*) = 1);
+DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/r/ibuf_not_empty.result b/mysql-test/suite/innodb/r/ibuf_not_empty.result
index d1b8203b063..f2da89990b0 100644
--- a/mysql-test/suite/innodb/r/ibuf_not_empty.result
+++ b/mysql-test/suite/innodb/r/ibuf_not_empty.result
@@ -5,6 +5,7 @@ c INT,
 INDEX(b))
 ENGINE=InnoDB STATS_PERSISTENT=0;
 SET GLOBAL innodb_change_buffering_debug = 1;
+SET GLOBAL innodb_change_buffering=all;
 INSERT INTO t1 SELECT 0,'x',1 FROM seq_1_to_1024;
 # restart: --innodb-force-recovery=6 --innodb-change-buffer-dump
 check table t1;
diff --git a/mysql-test/suite/innodb/r/innodb-change-buffer-recovery.result b/mysql-test/suite/innodb/r/innodb-change-buffer-recovery.result
index 678c8c67be5..f676d15b134 100644
--- a/mysql-test/suite/innodb/r/innodb-change-buffer-recovery.result
+++ b/mysql-test/suite/innodb/r/innodb-change-buffer-recovery.result
@@ -13,6 +13,7 @@ c INT,
 INDEX(b))
 ENGINE=InnoDB STATS_PERSISTENT=0;
 SET GLOBAL innodb_change_buffering_debug = 1;
+SET GLOBAL innodb_change_buffering = all;
 INSERT INTO t1 SELECT 0,'x',1 FROM seq_1_to_8192;
 BEGIN;
 SELECT b FROM t1 LIMIT 3;
diff --git a/mysql-test/suite/innodb/t/ibuf_not_empty.test b/mysql-test/suite/innodb/t/ibuf_not_empty.test
index 545a78c887e..96ceb81ac00 100644
--- a/mysql-test/suite/innodb/t/ibuf_not_empty.test
+++ b/mysql-test/suite/innodb/t/ibuf_not_empty.test
@@ -24,6 +24,7 @@ ENGINE=InnoDB STATS_PERSISTENT=0;
 # change buffering is possible, so that the change buffer will be used
 # whenever possible.
 SET GLOBAL innodb_change_buffering_debug = 1;
+SET GLOBAL innodb_change_buffering=all;
 
 # Create enough rows for the table, so that the change buffer will be
 # used for modifying the secondary index page. There must be multiple
diff --git a/mysql-test/suite/innodb/t/innodb-change-buffer-recovery.test b/mysql-test/suite/innodb/t/innodb-change-buffer-recovery.test
index a12ca43cec1..129037e783b 100644
--- a/mysql-test/suite/innodb/t/innodb-change-buffer-recovery.test
+++ b/mysql-test/suite/innodb/t/innodb-change-buffer-recovery.test
@@ -33,6 +33,7 @@ ENGINE=InnoDB STATS_PERSISTENT=0;
 # change buffering is possible, so that the change buffer will be used
 # whenever possible.
 SET GLOBAL innodb_change_buffering_debug = 1;
+SET GLOBAL innodb_change_buffering = all;
 let SEARCH_FILE = $MYSQLTEST_VARDIR/log/mysqld.1.err;
 
 # Create enough rows for the table, so that the change buffer will be
diff --git a/mysql-test/suite/innodb/t/innodb_defragment.test b/mysql-test/suite/innodb/t/innodb_defragment.test
index d9f5f56316e..51ef78377cb 100644
--- a/mysql-test/suite/innodb/t/innodb_defragment.test
+++ b/mysql-test/suite/innodb/t/innodb_defragment.test
@@ -1,6 +1,8 @@
 --source include/have_innodb.inc
 --source include/big_test.inc
 --source include/not_embedded.inc
+# Valgrind is to slow for this test
+--source include/not_valgrind.inc
 
 set global innodb_defragment_stats_accuracy = 80;
 
diff --git a/mysql-test/suite/sys_vars/r/innodb_change_buffering_basic.result b/mysql-test/suite/sys_vars/r/innodb_change_buffering_basic.result
index 92e22c6aa34..c11f4ee617c 100644
--- a/mysql-test/suite/sys_vars/r/innodb_change_buffering_basic.result
+++ b/mysql-test/suite/sys_vars/r/innodb_change_buffering_basic.result
@@ -1,28 +1,28 @@
 SET @start_global_value = @@global.innodb_change_buffering;
 SELECT @start_global_value;
 @start_global_value
-all
+none
 Valid values are 'all', 'deletes', 'changes', 'inserts', 'none', 'purges'
 select @@global.innodb_change_buffering in ('all', 'deletes', 'changes', 'inserts', 'none', 'purges');
 @@global.innodb_change_buffering in ('all', 'deletes', 'changes', 'inserts', 'none', 'purges')
 1
 select @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
-all
+none
 select @@session.innodb_change_buffering;
 ERROR HY000: Variable 'innodb_change_buffering' is a GLOBAL variable
 show global variables like 'innodb_change_buffering';
 Variable_name	Value
-innodb_change_buffering	all
+innodb_change_buffering	none
 show session variables like 'innodb_change_buffering';
 Variable_name	Value
-innodb_change_buffering	all
+innodb_change_buffering	none
 select * from information_schema.global_variables where variable_name='innodb_change_buffering';
 VARIABLE_NAME	VARIABLE_VALUE
-INNODB_CHANGE_BUFFERING	all
+INNODB_CHANGE_BUFFERING	none
 select * from information_schema.session_variables where variable_name='innodb_change_buffering';
 VARIABLE_NAME	VARIABLE_VALUE
-INNODB_CHANGE_BUFFERING	all
+INNODB_CHANGE_BUFFERING	none
 set global innodb_change_buffering='none';
 select @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
@@ -62,4 +62,4 @@ ERROR 42000: Variable 'innodb_change_buffering' can't be set to the value of 'so
 SET @@global.innodb_change_buffering = @start_global_value;
 SELECT @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
-all
+none
diff --git a/mysql-test/suite/sys_vars/r/sysvars_innodb.result b/mysql-test/suite/sys_vars/r/sysvars_innodb.result
index c0803ed765b..e8725e044f5 100644
--- a/mysql-test/suite/sys_vars/r/sysvars_innodb.result
+++ b/mysql-test/suite/sys_vars/r/sysvars_innodb.result
@@ -311,7 +311,7 @@ READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	OPTIONAL
 VARIABLE_NAME	INNODB_CHANGE_BUFFERING
 SESSION_VALUE	NULL
-DEFAULT_VALUE	all
+DEFAULT_VALUE	none
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	ENUM
 VARIABLE_COMMENT	Buffer changes to secondary indexes.
diff --git a/mysys/my_addr_resolve.c b/mysys/my_addr_resolve.c
index 0603a50fac7..444a47bb7c5 100644
--- a/mysys/my_addr_resolve.c
+++ b/mysys/my_addr_resolve.c
@@ -170,6 +170,7 @@ static pid_t pid;
 static char addr2line_binary[1024];
 static char output[1024];
 static struct pollfd poll_fds;
+static void *addr_offset;
 
 int start_addr2line_fork(const char *binary_path)
 {
@@ -297,7 +298,6 @@ static int addr_resolve(void *ptr, my_addr_loc *loc)
 int my_addr_resolve(void *ptr, my_addr_loc *loc)
 {
   Dl_info info;
-  int error;
 
   if (!dladdr(ptr, &info))
     return 1;
@@ -307,7 +307,7 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
     /*
       We use dli_fname in case the path is longer than the length of
       our static string. We don't want to allocate anything
-      dynamicaly here as we are in a "crashed" state.
+      dynamically here as we are in a "crashed" state.
     */
     if (start_addr2line_fork(info.dli_fname))
     {
@@ -318,10 +318,22 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
     }
     /* Save result for future comparisons. */
     strnmov(addr2line_binary, info.dli_fname, sizeof(addr2line_binary));
+
+    /*
+      Check if we should use info.dli_fbase as an offset or not
+      for the base program. This is depending on if the compilation is
+      done with PIE or not.
+    */
+    addr_offset= (void*) info.dli_fbase;
+#ifndef __PIE__
+    if (strcmp(info.dli_fname, my_progname) == 0 &&
+        addr_resolve((void*) my_addr_resolve, loc) == 0 &&
+	strcmp(loc->func, "my_addr_resolve") == 0)
+      addr_offset= 0;
+#endif
   }
-  if (!(error= addr_resolve((void*) (ptr - info.dli_fbase), loc)))
-    return 0;
-  return error;
+
+  return addr_resolve((void*) (ptr - addr_offset), loc);
 }
 
 
diff --git a/mysys/my_gethwaddr.c b/mysys/my_gethwaddr.c
index 70e1d549e15..46b62a0166d 100644
--- a/mysys/my_gethwaddr.c
+++ b/mysys/my_gethwaddr.c
@@ -23,6 +23,7 @@
 
 #ifndef MAIN
 
+#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__linux__) || defined(__sun) || defined(_WIN32)
 static my_bool memcpy_and_test(uchar *to, uchar *from, uint len)
 {
   uint i, res= 1;
@@ -32,6 +33,7 @@ static my_bool memcpy_and_test(uchar *to, uchar *from, uint len)
       res= 0;
   return res;
 }
+#endif
 
 #if defined(__APPLE__) || defined(__FreeBSD__)
 #include <net/ethernet.h>
@@ -195,4 +197,3 @@ int main(int argc __attribute__((unused)),char **argv)
   return 0;
 }
 #endif
-
diff --git a/sql/backup.cc b/sql/backup.cc
index 539dc9c31f4..c856048b49a 100644
--- a/sql/backup.cc
+++ b/sql/backup.cc
@@ -233,8 +233,12 @@ static bool backup_flush(THD *thd)
     This will probably require a callback from the InnoDB code.
 */
 
+/* Retry to get inital lock for 0.1 + 0.5 + 2.25 + 11.25 + 56.25 = 70.35 sec */
+#define MAX_RETRY_COUNT 5
+
 static bool backup_block_ddl(THD *thd)
 {
+  uint sleep_time;
   DBUG_ENTER("backup_block_ddl");
 
   kill_delayed_threads();
@@ -275,17 +279,32 @@ static bool backup_block_ddl(THD *thd)
     block new DDL's, in addition to all previous blocks
     We didn't do this lock above, as we wanted DDL's to be executed while
     we wait for non transactional tables (which may take a while).
+
+    We do this lock in a loop as we can get a deadlock if there are multi-object
+    ddl statements like
+    RENAME TABLE t1 TO t2, t3 TO t3
+    and the MDL happens in the middle of it.
  */
-  if (thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
-                                           MDL_BACKUP_WAIT_DDL,
-                                           thd->variables.lock_wait_timeout))
+  sleep_time= 100;                              // Start with 0.1 seconds
+  for (uint i= 0 ; i <= MAX_RETRY_COUNT ; i++)
   {
-    /*
-      Could be a timeout. Downgrade lock to what is was before this function
-      was called so that this function can be called again
-    */
-    backup_flush_ticket->downgrade_lock(MDL_BACKUP_FLUSH);
-    DBUG_RETURN(1);
+    if (!thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
+                                              MDL_BACKUP_WAIT_DDL,
+                                              thd->variables.lock_wait_timeout))
+      break;
+    if (thd->get_stmt_da()->sql_errno() != ER_LOCK_DEADLOCK || thd->killed ||
+        i == MAX_RETRY_COUNT)
+    {
+      /*
+        Could be a timeout. Downgrade lock to what is was before this function
+        was called so that this function can be called again
+      */
+      backup_flush_ticket->downgrade_lock(MDL_BACKUP_FLUSH);
+      DBUG_RETURN(1);
+    }
+    thd->clear_error();                         // Forget the DEADLOCK error
+    my_sleep(sleep_time);
+    sleep_time*= 5;                             // Wait a bit longer next time
   }
   DBUG_RETURN(0);
 }
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index 1744d5b58bf..e3287e1bbea 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -14039,7 +14039,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree, double read_time)
         key_part_range[1]= last_part;
 
         /* Check if cur_part is referenced in the WHERE clause. */
-        if (join->conds->walk(&Item::find_item_in_field_list_processor, 0,
+        if (join->conds->walk(&Item::find_item_in_field_list_processor, true,
                               key_part_range))
         {
           cause= "keypart reference from where clause";
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index a76eb2a4692..47e23a8b48d 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -1589,7 +1589,8 @@ bool JOIN::prepare_stage2()
 #endif
   if (select_lex->olap == ROLLUP_TYPE && rollup_init())
     goto err;
-  if (alloc_func_list())
+  if (alloc_func_list() ||
+      make_sum_func_list(all_fields, fields_list, false))
     goto err;
 
   res= FALSE;
@@ -2204,7 +2205,21 @@ JOIN::optimize_inner()
       If all items were resolved by opt_sum_query, there is no need to
       open any tables.
     */
-    if ((res=opt_sum_query(thd, select_lex->leaf_tables, all_fields, conds)))
+
+    /*
+      The following resetting and restoring of sum_funcs is needed to
+      go around a bug in spider where it assumes that
+      make_sum_func_list() has not been called yet and do logical
+      choices based on this if special handling of min/max functions should
+      be done. We disable this special handling while we are trying to find
+      out if we can replace MIN/MAX values with constants.
+    */
+    Item_sum **save_func_sums= sum_funcs, *tmp_sum_funcs= 0;
+    sum_funcs= &tmp_sum_funcs;
+    res= opt_sum_query(thd, select_lex->leaf_tables, all_fields, conds);
+    sum_funcs= save_func_sums;
+
+    if (res)
     {
       DBUG_ASSERT(res >= 0);
       if (res == HA_ERR_KEY_NOT_FOUND)
@@ -2776,13 +2791,15 @@ int JOIN::optimize_stage2()
     calc_group_buffer(this, group_list);
   }
 
-  if (test_if_subpart(group_list, order) ||
-      (!group_list && tmp_table_param.sum_func_count))
-  {
+  /*
+    We can ignore ORDER BY if it's a prefix of the GROUP BY list
+    (as MariaDB is by default sorting on GROUP BY) or
+    if there is no GROUP BY and aggregate functions are used
+    (as the result will only contain one row).
+  */
+  if (order && (test_if_subpart(group_list, order) ||
+                (!group_list && tmp_table_param.sum_func_count)))
     order=0;
-    if (is_indexed_agg_distinct(this, NULL))
-      sort_and_group= 0;
-  }
 
   // Can't use sort on head table if using join buffering
   if (full_join || hash_join)
@@ -2814,7 +2831,6 @@ int JOIN::optimize_stage2()
   if (select_lex->have_window_funcs())
     simple_order= FALSE;
 
-
   /*
     If the hint FORCE INDEX FOR ORDER BY/GROUP BY is used for the table
     whose columns are required to be returned in a sorted order, then
@@ -3548,7 +3564,7 @@ bool JOIN::make_aggr_tables_info()
       // for the first table
       if (group_list || tmp_table_param.sum_func_count)
       {
-        if (make_sum_func_list(*curr_all_fields, *curr_fields_list, true, true))
+        if (make_sum_func_list(*curr_all_fields, *curr_fields_list, true))
           DBUG_RETURN(true);
         if (prepare_sum_aggregators(sum_funcs,
                                     !join_tab->is_using_agg_loose_index_scan()))
@@ -3658,7 +3674,7 @@ bool JOIN::make_aggr_tables_info()
       last_tab->all_fields= &tmp_all_fields3;
       last_tab->fields= &tmp_fields_list3;
     }
-    if (make_sum_func_list(*curr_all_fields, *curr_fields_list, true, true))
+    if (make_sum_func_list(*curr_all_fields, *curr_fields_list, true))
       DBUG_RETURN(true);
     if (prepare_sum_aggregators(sum_funcs,
                                 !join_tab ||
@@ -3854,8 +3870,6 @@ JOIN::create_postjoin_aggr_table(JOIN_TAB *tab, List<Item> *table_fields,
   }
   else
   {
-    if (make_sum_func_list(all_fields, fields_list, false))
-      goto err;
     if (prepare_sum_aggregators(sum_funcs,
                                 !join_tab->is_using_agg_loose_index_scan()))
       goto err;
@@ -7097,8 +7111,7 @@ void optimize_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse_array)
   Check for the presence of AGGFN(DISTINCT a) queries that may be subject
   to loose index scan.
 
-
-  Check if the query is a subject to AGGFN(DISTINCT) using loose index scan 
+  Check if the query is a subject to AGGFN(DISTINCT) using loose index scan
   (QUICK_GROUP_MIN_MAX_SELECT).
   Optionally (if out_args is supplied) will push the arguments of 
   AGGFN(DISTINCT) to the list
@@ -7131,14 +7144,11 @@ is_indexed_agg_distinct(JOIN *join, List<Item_field> *out_args)
   Item_sum **sum_item_ptr;
   bool result= false;
 
-  if (join->table_count != 1 ||                    /* reference more than 1 table */
+  if (join->table_count != 1 ||               /* reference more than 1 table */
       join->select_distinct ||                /* or a DISTINCT */
       join->select_lex->olap == ROLLUP_TYPE)  /* Check (B3) for ROLLUP */
     return false;
 
-  if (join->make_sum_func_list(join->all_fields, join->fields_list, true))
-    return false;
-
   Bitmap<MAX_FIELDS> first_aggdistinct_fields;
   bool first_aggdistinct_fields_initialized= false;
   for (sum_item_ptr= join->sum_funcs; *sum_item_ptr; sum_item_ptr++)
@@ -7240,16 +7250,23 @@ add_group_and_distinct_keys(JOIN *join, JOIN_TAB *join_tab)
     while ((item= select_items_it++))
       item->walk(&Item::collect_item_field_processor, 0, &indexed_fields);
   }
-  else if (join->tmp_table_param.sum_func_count &&
-           is_indexed_agg_distinct(join, &indexed_fields))
+  else if (!join->tmp_table_param.sum_func_count ||
+           !is_indexed_agg_distinct(join, &indexed_fields))
   {
-    join->sort_and_group= 1;
-  }
-  else
+    /*
+      There where no GROUP BY fields and also either no aggregate
+      functions or not all aggregate functions where used with the
+      same DISTINCT (or MIN() / MAX() that works similarly).
+      Nothing to do there.
+    */
     return;
+  }
 
   if (indexed_fields.elements == 0)
+  {
+    /* There where no index we could use to satisfy the GROUP BY */
     return;
+  }
 
   /* Intersect the keys of all group fields. */
   cur_item= indexed_fields_it++;
@@ -25693,16 +25710,13 @@ bool JOIN::alloc_func_list()
 
 bool JOIN::make_sum_func_list(List<Item> &field_list,
                               List<Item> &send_result_set_metadata,
-			      bool before_group_by, bool recompute)
+			      bool before_group_by)
 {
   List_iterator_fast<Item> it(field_list);
   Item_sum **func;
   Item *item;
   DBUG_ENTER("make_sum_func_list");
 
-  if (*sum_funcs && !recompute)
-    DBUG_RETURN(FALSE); /* We have already initialized sum_funcs. */
-
   func= sum_funcs;
   while ((item=it++))
   {
@@ -25849,7 +25863,7 @@ change_to_use_tmp_fields(THD *thd, Ref_ptr_array ref_pointer_array,
   Change all funcs to be fields in tmp table.
 
   @param thd                   THD pointer
-  @param ref_pointer_array     array of pointers to top elements of filed list
+  @param ref_pointer_array     array of pointers to top elements of field list
   @param res_selected_fields   new list of items of select item list
   @param res_all_fields        new list of all items
   @param elements              number of elements in select item list
diff --git a/sql/sql_select.h b/sql/sql_select.h
index 24a2ccd8ec1..81354b4c42c 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -1196,7 +1196,17 @@ public:
     Indicates that grouping will be performed on the result set during
     query execution. This field belongs to query execution.
 
-    @see make_group_fields, alloc_group_fields, JOIN::exec
+    If 'sort_and_group' is set, then the optimizer is going to use on of
+    the following algorithms to resolve GROUP BY.
+
+    - If one table, sort the table and then calculate groups on the fly.
+    - If more than one table, create a temporary table to hold the join,
+      sort it and then resolve group by on the fly.
+
+    The 'on the fly' calculation is done in end_send_group()
+
+    @see make_group_fields, alloc_group_fields, JOIN::exec,
+         setup_end_select_func
   */
   bool     sort_and_group; 
   bool     first_record,full_join, no_field_update;
@@ -1654,7 +1664,7 @@ public:
   bool make_range_rowid_filters();
   bool init_range_rowid_filters();
   bool make_sum_func_list(List<Item> &all_fields, List<Item> &send_fields,
-			  bool before_group_by, bool recompute= FALSE);
+			  bool before_group_by);
 
   /// Initialzes a slice, see comments for ref_ptrs above.
   Ref_ptr_array ref_ptr_array_slice(size_t slice_num)
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index b4a3b423df6..b9f2ea67632 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -19659,7 +19659,7 @@ static MYSQL_SYSVAR_BOOL(numa_interleave, srv_numa_interleave,
 static MYSQL_SYSVAR_ENUM(change_buffering, innodb_change_buffering,
   PLUGIN_VAR_RQCMDARG,
   "Buffer changes to secondary indexes.",
-  NULL, NULL, IBUF_USE_ALL, &innodb_change_buffering_typelib);
+  NULL, NULL, IBUF_USE_NONE, &innodb_change_buffering_typelib);
 
 static MYSQL_SYSVAR_UINT(change_buffer_max_size,
   srv_change_buffer_max_size,
diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index 914337d2a54..cee2fa978ab 100644
--- a/storage/innobase/log/log0log.cc
+++ b/storage/innobase/log/log0log.cc
@@ -639,8 +639,7 @@ loop:
 	}
 }
 
-/** Flush the recently written changes to the log file.
-and invoke mysql_mutex_lock(&log_sys.mutex). */
+/** Flush the recently written changes to the log file.*/
 static void log_write_flush_to_disk_low(lsn_t lsn)
 {
   if (!log_sys.log.writes_are_durable())
@@ -780,10 +779,6 @@ static void log_write(bool rotate_key)
 		start_offset - area_start);
 	srv_stats.log_padded.add(pad_size);
 	log_sys.write_lsn = write_lsn;
-	if (log_sys.log.writes_are_durable()) {
-		log_sys.set_flushed_lsn(write_lsn);
-		log_flush_notify(write_lsn);
-	}
 	return;
 }