MDEV-15152 Optimistic parallel slave doesnt cope well with START SLAVE UNTIL

The immediate bug was caused by a failure to recognize a correct
position to stop the slave applier run in optimistic parallel mode.
There were the following set of issues that the analysis unveil.
1 incorrect estimate for the event binlog position passed to
  is_until_satisfied
2 wait for workers to complete by the driver thread did not account non-group events
  that could be left unprocessed and thus to mix up the last executed
  binlog group's file and position:
  the file remained old and the position related to the new rotated file
3 incorrect 'slave reached file:pos' by the parallel slave report in the error log
4 relay log UNTIL missed out the parallel slave branch in
  is_until_satisfied.

The patch addresses all of them to simplify logics of log change
notification in either the master and relay-log until case.
P.1 is addressed with passing the event into is_until_satisfied()
for proper analisis by the function.
P.2 is fixed by changes in handle_queued_pos_update().
P.4 required removing relay-log change notification by workers.
Instead the driver thread updates the notion of the current relay-log
fully itself with aid of introduced
bool Relay_log_info::until_relay_log_names_defer.

An extra print out of the requested until file:pos is arranged
with --log-warning=3.

6 files changed, 859 insertions, 20 deletions

diff --git a/mysql-test/suite/rpl/r/rpl_parallel_optimistic_until.result b/mysql-test/suite/rpl/r/rpl_parallel_optimistic_until.result
new file mode 100644
index 00000000000..a83a9b61b9f
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_parallel_optimistic_until.result
@@ -0,0 +1,291 @@
+include/master-slave.inc
+[connection master]
+connection slave;
+include/stop_slave.inc
+RESET MASTER;
+RESET SLAVE;
+connection master;
+RESET MASTER;
+CREATE TABLE t1 (a int primary key, b text) ENGINE=InnoDB;
+INSERT INTO t1 SET a=25, b='trx0';
+connection slave;
+include/start_slave.inc
+connection master;
+connection slave;
+include/stop_slave.inc
+ALTER TABLE mysql.gtid_slave_pos ENGINE=InnoDB;
+SET @old_parallel_threads=@@GLOBAL.slave_parallel_threads;
+SET GLOBAL slave_parallel_threads=2;
+SET @old_parallel_mode=@@GLOBAL.slave_parallel_mode;
+SET GLOBAL slave_parallel_mode='optimistic';
+connection slave;
+SET @old_max_relay_log_size = @@global.max_relay_log_size;
+SET @@global.max_relay_log_size=4096;
+connection master;
+BEGIN;
+INSERT INTO t1 SET a=1, b='trx1';
+INSERT INTO t1 SET a=2, b='trx1';
+INSERT INTO t1 SET a=3, b='trx1';
+INSERT INTO t1 SET a=4, b='trx1';
+INSERT INTO t1 SET a=5, b='trx1';
+INSERT INTO t1 SET a=6, b='trx1';
+INSERT INTO t1 SET a=7, b='trx1';
+INSERT INTO t1 SET a=8, b='trx1';
+INSERT INTO t1 SET a=9, b='trx1';
+INSERT INTO t1 SET a=10, b='trx1';
+INSERT INTO t1 SET a=11, b='trx1';
+INSERT INTO t1 SET a=12, b='trx1';
+INSERT INTO t1 SET a=13, b='trx1';
+INSERT INTO t1 SET a=14, b='trx1';
+INSERT INTO t1 SET a=15, b='trx1';
+INSERT INTO t1 SET a=16, b='trx1';
+INSERT INTO t1 SET a=17, b='trx1';
+INSERT INTO t1 SET a=18, b='trx1';
+INSERT INTO t1 SET a=19, b='trx1';
+INSERT INTO t1 SET a=20, b='trx1';
+INSERT INTO t1 SET a=21, b='trx1';
+INSERT INTO t1 SET a=22, b='trx1';
+INSERT INTO t1 SET a=23, b='trx1';
+INSERT INTO t1 SET a=24, b='trx1';
+COMMIT;
+FLUSH LOGS;
+BEGIN;
+UPDATE t1 SET b='trx2_0' WHERE a = 25;
+UPDATE t1 SET b='trx2' WHERE a = 25;
+COMMIT;
+INSERT INTO t1 SET a=26,b='trx3';
+*** case 1 UNTIL inside trx2
+connection slave1;
+BEGIN;
+INSERT INTO t1 SET a= 1;
+connection slave;
+SELECT <pos_0> <= <pos_until> AND <pos_until> < <pos_trx2> as "pos_until < trx0 and is within trx2";
+pos_until < trx0 and is within trx2
+1
+CHANGE MASTER TO MASTER_USE_GTID=no;
+START SLAVE UNTIL MASTER_LOG_FILE = 'file_2', MASTER_LOG_POS = <pos_until>;
+connection slave1;
+ROLLBACK;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+SELECT count(*) = 1 as 'trx2 is committed' FROM t1 WHERE b = 'trx2';
+trx2 is committed
+1
+SELECT count(*) = 0 as 'trx3 is not committed' FROM t1 WHERE b = 'trx3';
+trx3 is not committed
+1
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+*** case 2 UNTIL inside trx2
+connection slave;
+DELETE FROM t1 WHERE a <> 25;
+UPDATE t1 SET b='trx0' WHERE a = 25;
+connection slave1;
+BEGIN;
+INSERT INTO t1 SET a= 1;
+connection slave;
+include/stop_slave.inc
+SELECT <pos_0> <= <pos_until> AND <pos_until> < <pos_trx2> as "pos_until >= trx0 and is within trx2";
+pos_until >= trx0 and is within trx2
+1
+CHANGE MASTER TO MASTER_LOG_FILE = 'file_1', MASTER_LOG_POS = <pos_trx0>, MASTER_USE_GTID=no;
+START SLAVE UNTIL MASTER_LOG_FILE = 'file_2', MASTER_LOG_POS = <pos_until>;
+connection slave1;
+ROLLBACK;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+SELECT count(*) = 1 as 'trx2 is committed' FROM t1 WHERE b = 'trx2';
+trx2 is committed
+1
+SELECT count(*) = 0 as 'trx3 is not committed' FROM t1 WHERE b = 'trx3';
+trx3 is not committed
+1
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+*** case 3 UNTIL inside trx1
+connection slave;
+DELETE FROM t1 WHERE a <> 25;
+UPDATE t1 SET b='trx0' WHERE a = 25;
+connection slave1;
+BEGIN;
+INSERT INTO t1 SET a= 1; # block trx1;
+connection slave;
+include/stop_slave.inc
+SELECT <pos_until> < <pos_0> as "pos_until before trx2 start position";
+pos_until before trx2 start position
+1
+CHANGE MASTER TO MASTER_LOG_FILE = 'file_1', MASTER_LOG_POS = <pos_trx0>, MASTER_USE_GTID=no;
+START SLAVE UNTIL MASTER_LOG_FILE = 'file_2', MASTER_LOG_POS = <pos_until>;
+connection slave1;
+ROLLBACK;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+SELECT count(*) = 25-1 as 'trx1 is committed' FROM t1 WHERE b = 'trx1';
+trx1 is committed
+1
+SELECT count(*) = 0 as 'trx2 is not committed' FROM t1 WHERE b = 'trx2';
+trx2 is not committed
+1
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+*** case 4 Relay-log UNTIL inside trx1
+connection slave;
+DELETE FROM t1 WHERE a <> 25;
+UPDATE t1 SET b='trx0' WHERE a = 25;
+connection slave1;
+BEGIN;
+INSERT INTO t1 SET a= 1; # block trx1;
+connection slave;
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_LOG_FILE = 'file_1', MASTER_LOG_POS = <pos_trx0>, MASTER_USE_GTID=no;
+START SLAVE IO_THREAD;
+include/wait_for_slave_io_to_start.inc
+START SLAVE UNTIL RELAY_LOG_FILE = 'file_2', RELAY_LOG_POS = <pos_until>;
+connection slave1;
+ROLLBACK;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+SELECT count(*) = 25-1 as 'trx1 is committed' FROM t1 WHERE b = 'trx1';
+trx1 is committed
+1
+SELECT count(*) = 0 as 'trx2 is not committed' FROM t1 WHERE b = 'trx2';
+trx2 is not committed
+1
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+*** case 5 Relay-log UNTIL inside a "big" trx that spawns few relay logs
+connection master;
+CREATE TABLE t2 (a TEXT) ENGINE=InnoDB;
+FLUSH LOGS;
+connection slave;
+connection slave;
+include/stop_slave.inc
+connection master;
+BEGIN;
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+INSERT INTO t2 SET a=repeat('a',1024);
+COMMIT;
+INSERT INTO t2 SET a='a';
+connection slave;
+START SLAVE IO_THREAD;
+include/wait_for_slave_io_to_start.inc
+START SLAVE UNTIL RELAY_LOG_FILE = 'file_2', RELAY_LOG_POS = <pos_until>;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+include/diff_tables.inc [master:t2,slave:t2]
+*** case 6 Relay-log UNTIL inside a small trx inside a sequence of relay logs
+connection slave;
+include/stop_slave.inc
+connection master;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+BEGIN;
+DELETE FROM t2 LIMIT 1;
+COMMIT;
+COMMIT;
+connection slave;
+START SLAVE IO_THREAD;
+include/wait_for_slave_io_to_start.inc
+connection master;
+include/sync_slave_io_with_master.inc
+connection slave;
+START SLAVE UNTIL RELAY_LOG_FILE = 'file_2', RELAY_LOG_POS = <pos_until>;
+Proof 1: Correct stop
+connection slave;
+include/wait_for_slave_sql_to_stop.inc
+Proof 2: Resume works out
+include/start_slave.inc
+connection master;
+connection slave;
+include/diff_tables.inc [master:t2,slave:t2]
+connection slave;
+include/stop_slave.inc
+SET GLOBAL max_relay_log_size=@old_max_relay_log_size;
+SET GLOBAL slave_parallel_mode=@old_parallel_mode;
+SET GLOBAL slave_parallel_threads=@old_parallel_threads;
+include/start_slave.inc
+connection master;
+DROP TABLE t1, t2;
+connection slave;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_parallel_optimistic_until.test b/mysql-test/suite/rpl/t/rpl_parallel_optimistic_until.test
new file mode 100644
index 00000000000..508213c9075
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_parallel_optimistic_until.test
@@ -0,0 +1,465 @@
+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+--source include/master-slave.inc
+# Format is restricted because the test expects a specific result of
+# relay-logging that splits a transaction into two different files.
+--source include/have_binlog_format_row.inc
+
+#
+# MDEV-15152 Optimistic parallel slave doesn't cope well with START SLAVE UNTIL
+#
+--connection slave
+--source include/stop_slave.inc
+RESET MASTER;
+RESET SLAVE;
+
+--connection master
+RESET MASTER;
+CREATE TABLE t1 (a int primary key, b text) ENGINE=InnoDB;
+--let $a0 = 25
+--eval INSERT INTO t1 SET a=$a0, b='trx0'
+# Memorize the position for replication restart from it
+--let $pos_trx0 = query_get_value(SHOW MASTER STATUS, Position, 1)
+
+--connection slave
+--source include/start_slave.inc
+
+--connection master
+# --connection slave
+--sync_slave_with_master
+--source include/stop_slave.inc
+ALTER TABLE mysql.gtid_slave_pos ENGINE=InnoDB;
+SET @old_parallel_threads=@@GLOBAL.slave_parallel_threads;
+SET GLOBAL slave_parallel_threads=2;
+SET @old_parallel_mode=@@GLOBAL.slave_parallel_mode;
+SET GLOBAL slave_parallel_mode='optimistic';
+
+# Run the slave in the following modes one by one.
+#
+# 1. the until position is set in the middle of trx2
+#    below $pos_trx0 of the last exec position in the first file
+# 2. and above $pos_trx0
+#    In either case trx2 must commit before slave stops.
+# 3. the until postion is inside trx1
+# 4. RELAY log until inside trx1
+# 5. RELAY log until inside a "big" trx
+# 6. RELAY log until inside a trx within a sequence of relay logs
+#
+# Execution flaw for Until_Master_Pos cases follows as:
+# create the transaction trx1, trx2
+# logged at the beginning of two subsequent binlog files.
+# Set the until position to at the middle of the 2rd transaction.
+# Engage the optimistic scheduler while having trx1 execution blocked.
+# Lift the block after trx2 has reached waiting its order to commit.
+# *Proof 1*
+#  Observe that the slave applier stops at a correct position.
+#   In the bug condition it would stop prematurely having the stop position
+#   in the first file, therefore trx2 not committed.
+# Specifically, an internal transaction position until makes the applier to run
+# beyond it to commit commit the current transaction.
+# *Proof 2*
+# Observe the following START SLAVE resumes OK.
+#
+# Auxiliary third trx3 on master is just for triggering the actual stop
+# (whihc is a legacy UNTIL's property).
+# trx0 is to produce a specific value of the last executed binlog file:pos
+# to emulate the bug condition.
+#
+# Intermediate checks via SELECT are supposed to succeed
+# with putting out value 1.
+#
+# NOTE: Relay log until tests have to use explicit log names and position
+# which may require to adjust with future changes to event formats etc.
+#
+
+--connection slave
+SET @old_max_relay_log_size = @@global.max_relay_log_size;
+SET @@global.max_relay_log_size=4096;
+
+--connection master
+# trx1
+--let $a=1
+BEGIN;
+while (`SELECT $a < $a0`)
+{
+  --eval INSERT INTO t1 SET a=$a, b='trx1'
+--inc $a
+}
+COMMIT;
+--let $fil_1    = query_get_value(SHOW MASTER STATUS, File, 1)
+--let $pos_trx1 = query_get_value(SHOW MASTER STATUS, Position, 1)
+
+FLUSH LOGS;
+
+# $pos_0 the offset of the first event of trx2 in new file
+--let $pos_0=query_get_value(SHOW MASTER STATUS, Position, 1)
+# trx2
+--let $a=$a0
+BEGIN;
+--eval UPDATE t1 SET b='trx2_0' WHERE a = $a
+--eval UPDATE t1 SET b='trx2' WHERE a = $a
+COMMIT;
+--let $fil_2=query_get_value(SHOW MASTER STATUS, File, 1)
+--let $pos_trx2=query_get_value(SHOW MASTER STATUS, Position, 1)
+
+# trx3
+--let $a=$a0
+--inc $a
+--eval INSERT INTO t1 SET a=$a,b='trx3'
+--let $pos_trx3=query_get_value(SHOW MASTER STATUS, Position, 1)
+--let $a=
+
+
+--echo *** case 1 UNTIL inside trx2
+
+--connection slave1
+# Blocker to hold off EXEC_MASTER_LOG_POS advance
+BEGIN;
+  --eval INSERT INTO t1 SET a= 1
+--connection slave
+--let $pos_until=`SELECT $pos_trx0 - 1`
+--replace_result $pos_0 <pos_0> $pos_until <pos_until> $pos_trx2 <pos_trx2>
+--eval SELECT $pos_0 <= $pos_until AND $pos_until < $pos_trx2 as "pos_until < trx0 and is within trx2"
+CHANGE MASTER TO MASTER_USE_GTID=no;
+--replace_result $fil_2 file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL MASTER_LOG_FILE = '$fil_2', MASTER_LOG_POS = $pos_until
+
+--let $wait_condition= SELECT COUNT(*) > 0 FROM information_schema.processlist WHERE state = "Waiting for prior transaction to commit"
+--source include/wait_condition.inc
+
+--connection slave1
+# unblock to see the slave applier stops at $until
+ROLLBACK;
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Master_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Exec_Master_Log_Pos, 1)
+if (`SELECT "$file_stop" != "$fil_2" OR $pos_stop < $pos_until`)
+{
+  --echo *** ERROR: Slave stopped at $file_stop:$pos_stop which is not $fil_2:$pos_until.
+  --die
+}
+--eval SELECT count(*) = 1 as 'trx2 is committed' FROM t1 WHERE b = 'trx2'
+--eval SELECT count(*) = 0 as 'trx3 is not committed' FROM t1 WHERE b = 'trx3'
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+
+--echo *** case 2 UNTIL inside trx2
+
+--connection slave
+--eval DELETE FROM t1 WHERE a <> $a0
+--eval UPDATE t1 SET b='trx0' WHERE a = $a0
+
+--connection slave1
+# Blocker to hold off EXEC_MASTER_LOG_POS advance
+BEGIN;
+  --eval INSERT INTO t1 SET a= 1
+
+--connection slave
+--source include/stop_slave.inc
+
+--let $pos_until=`SELECT $pos_trx2 - 1`
+--replace_result $pos_trx0 <pos_0> $pos_until <pos_until> $pos_trx2 <pos_trx2>
+--eval SELECT $pos_trx0 <= $pos_until AND $pos_until < $pos_trx2 as "pos_until >= trx0 and is within trx2"
+--replace_result $fil_1 file_1 $pos_trx0 <pos_trx0>
+--eval CHANGE MASTER TO MASTER_LOG_FILE = '$fil_1', MASTER_LOG_POS = $pos_trx0, MASTER_USE_GTID=no
+--replace_result  $fil_2 file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL MASTER_LOG_FILE = '$fil_2', MASTER_LOG_POS = $pos_until
+
+--let $wait_condition= SELECT COUNT(*) > 0 FROM information_schema.processlist WHERE state = "Waiting for prior transaction to commit"
+--source include/wait_condition.inc
+
+--connection slave1
+# unblock to see the slave applier stops at $until
+ROLLBACK;
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Master_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Exec_Master_Log_Pos, 1)
+if (`SELECT "$file_stop" != "$fil_2" OR $pos_stop < $pos_until`)
+{
+  --echo *** ERROR: Slave stopped at $file_stop:$pos_stop which is not $fil_2:$pos_until.
+  --die
+}
+--eval SELECT count(*) = 1 as 'trx2 is committed' FROM t1 WHERE b = 'trx2'
+--eval SELECT count(*) = 0 as 'trx3 is not committed' FROM t1 WHERE b = 'trx3'
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+
+--echo *** case 3 UNTIL inside trx1
+
+--connection slave
+--eval DELETE FROM t1 WHERE a <> $a0
+--eval UPDATE t1 SET b='trx0' WHERE a = $a0
+
+
+--connection slave1
+# Blocker to hold off EXEC_MASTER_LOG_POS advance
+BEGIN;
+  --eval INSERT INTO t1 SET a= 1; # block trx1
+
+--connection slave
+--source include/stop_slave.inc
+
+--let $pos_until=`SELECT $pos_0 - 1`
+--replace_result $pos_0 <pos_0> $pos_until <pos_until> $pos_trx2 <pos_trx2>
+--eval SELECT $pos_until < $pos_0 as "pos_until before trx2 start position"
+--replace_result $fil_1 file_1 $pos_trx0 <pos_trx0>
+--eval CHANGE MASTER TO MASTER_LOG_FILE = '$fil_1', MASTER_LOG_POS = $pos_trx0, MASTER_USE_GTID=no
+--replace_result  $fil_2 file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL MASTER_LOG_FILE = '$fil_2', MASTER_LOG_POS = $pos_until
+
+--connection slave1
+# unblock to see the slave applier stops at $until
+ROLLBACK;
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Master_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Exec_Master_Log_Pos, 1)
+if (`SELECT "$file_stop" != "$fil_2" OR $pos_stop < $pos_until`)
+{
+  --echo *** ERROR: Slave stopped at $file_stop:$pos_stop which is not $fil_2:$pos_until.
+  --die
+}
+--eval SELECT count(*) = $a0-1 as 'trx1 is committed' FROM t1 WHERE b = 'trx1'
+--eval SELECT count(*) = 0 as 'trx2 is not committed' FROM t1 WHERE b = 'trx2'
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+
+--echo *** case 4 Relay-log UNTIL inside trx1
+
+--connection slave
+--eval DELETE FROM t1 WHERE a <> $a0
+--eval UPDATE t1 SET b='trx0' WHERE a = $a0
+
+--connection slave1
+# Blocker to hold off EXEC_MASTER_LOG_POS advance
+BEGIN;
+  --eval INSERT INTO t1 SET a= 1; # block trx1
+
+--connection slave
+--source include/stop_slave.inc
+--replace_result $fil_1 file_1 $pos_trx0 <pos_trx0>
+--eval CHANGE MASTER TO MASTER_LOG_FILE = '$fil_1', MASTER_LOG_POS = $pos_trx0, MASTER_USE_GTID=no
+START SLAVE IO_THREAD;
+--source include/wait_for_slave_io_to_start.inc
+
+# The following test sets the stop coordinate is set to inside the first event
+# of a relay log that holds events of a transaction started in an earlier log.
+# Peek the stop position in the middle of trx1, not even on a event boundary.
+--let $pos_until=255
+--let $file_rl=slave-relay-bin.000003
+--let $binlog_file=$file_rl
+
+--let $pos_xid=508
+--let $info= query_get_value(SHOW RELAYLOG EVENTS IN '$file_rl' FROM $pos_xid LIMIT 1, Info, 1)
+
+if (`SELECT "$info" NOT LIKE "COMMIT /* xid=% */" OR $pos_xid < $pos_until`)
+{
+  --echo *** Unexpected offset. Refine it to point to the correct XID event!
+  --die
+}
+
+--replace_result  $file_rl file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL RELAY_LOG_FILE = '$file_rl', RELAY_LOG_POS = $pos_until
+
+--connection slave1
+# unblock to see the slave applier stops at $until
+ROLLBACK;
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Relay_Log_Pos, 1)
+if (`SELECT strcmp("$file_rl","$file_stop") > -1`)
+{
+  --echo *** ERROR: Slave stopped at $file_stop:$pos_stop which is not $file_rl:$pos_until.
+  --die
+}
+
+--eval SELECT count(*) = $a0-1 as 'trx1 is committed' FROM t1 WHERE b = 'trx1'
+--eval SELECT count(*) = 0 as 'trx2 is not committed' FROM t1 WHERE b = 'trx2'
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+
+
+--echo *** case 5 Relay-log UNTIL inside a "big" trx that spawns few relay logs
+
+--connection master
+CREATE TABLE t2 (a TEXT) ENGINE=InnoDB;
+FLUSH LOGS;
+
+--sync_slave_with_master
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Relay_Log_Pos, 1)
+--let $records=`SELECT floor(4*@@global.max_relay_log_size / 1024) + 1`
+
+--connection slave
+--source include/stop_slave.inc
+
+--connection master
+# trx4
+BEGIN;
+--let $i=$records
+while ($i)
+{
+ INSERT INTO t2 SET a=repeat('a',1024);
+
+--dec $i
+}
+COMMIT;
+
+# slave will stop there:
+--let $file_trx4 = query_get_value(SHOW MASTER STATUS, File, 1)
+--let $pos_trx4  = query_get_value(SHOW MASTER STATUS, Position, 1)
+
+# trx5
+INSERT INTO t2 SET a='a';
+--let $pos_trx5  = query_get_value(SHOW MASTER STATUS, Position, 1)
+
+--connection slave
+START SLAVE IO_THREAD;
+--source include/wait_for_slave_io_to_start.inc
+
+# Set position inside the transaction though the value
+# specified is beyond that relay log file.
+# The coordianate may point to in a different event in future changes
+# but should not move away from inside this big group of events.
+# So we don't test which event in the transaction it points to.
+--let $pos_until= 4500
+--let $file_rl= slave-relay-bin.000010
+
+--replace_result  $file_rl file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL RELAY_LOG_FILE = '$file_rl', RELAY_LOG_POS = $pos_until
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Master_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Exec_Master_Log_Pos, 1)
+# It's showed the actual stop occurred before trx5
+if (`SELECT strcmp("$file_trx4", "$file_stop") <> 0 OR $pos_stop >= $pos_trx5 OR count(*) <> $records FROM t2`)
+{
+  --echo *** ERROR: Slave stopped at *binlog* $file_stop:$pos_stop which is not $file_trx4:$pos_trx4.
+  --die
+}
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+--let $diff_tables=master:t2,slave:t2
+--source include/diff_tables.inc
+
+
+
+--echo *** case 6 Relay-log UNTIL inside a small trx inside a sequence of relay logs
+
+--connection slave
+--source include/stop_slave.inc
+
+--connection master
+# trx6
+--let $records=`SELECT count(*) FROM t2`
+while ($records)
+{
+  BEGIN;
+    DELETE FROM t2 LIMIT 1;
+  COMMIT;
+--dec $records
+}
+COMMIT;
+
+--connection slave
+START SLAVE IO_THREAD;
+--source include/wait_for_slave_io_to_start.inc
+
+--connection master
+--source include/sync_slave_io_with_master.inc
+
+--connection slave
+# The relay-log coordinate is not at an event boundary and
+# also may change across the server version.
+# The test makes its best to check its coherance.
+--let $pos_until= 3130
+--let $file_rl= slave-relay-bin.000018
+
+--let $pos_gtid = 2987
+--let $info= query_get_value(SHOW RELAYLOG EVENTS IN '$file_rl' FROM $pos_gtid LIMIT 1, Info, 1)
+
+if (`SELECT "$info" != "BEGIN GTID 0-1-23"`)
+{
+  --echo *** Unexpected offset. Refine it to point to the correct GTID!
+  --die
+}
+--let $pos_event = 3120
+--let $type= query_get_value(SHOW RELAYLOG EVENTS IN '$file_rl' FROM $pos_event LIMIT 1, Event_type, 1)
+if (`SELECT "$type" != "Delete_rows_v1"`)
+{
+  --echo *** Unexpected offset. Refine it to point to the expected event!
+  --die
+}
+
+--replace_result  $file_rl file_2 $pos_until <pos_until>
+--eval START SLAVE UNTIL RELAY_LOG_FILE = '$file_rl', RELAY_LOG_POS = $pos_until
+
+--echo Proof 1: Correct stop
+--connection slave
+--source include/wait_for_slave_sql_to_stop.inc
+--let $file_stop= query_get_value(SHOW SLAVE STATUS, Relay_Log_File, 1)
+--let $pos_stop=  query_get_value(SHOW SLAVE STATUS, Relay_Log_Pos, 1)
+if (`SELECT strcmp("$file_stop", "$file_rl") = -1 OR
+            strcmp("$file_stop", "$file_rl") =  0 AND $pos_stop < $pos_until`)
+{
+  --echo *** ERROR: Slave stopped at *relay* $file_stop:$pos_stop which is not $file_rl:$pos_until.
+  --die
+}
+
+--echo Proof 2: Resume works out
+--source include/start_slave.inc
+--connection master
+--sync_slave_with_master
+
+--let $diff_tables=master:t2,slave:t2
+--source include/diff_tables.inc
+
+#
+# Clean up.
+#
+--connection slave
+--source include/stop_slave.inc
+SET GLOBAL max_relay_log_size=@old_max_relay_log_size;
+SET GLOBAL slave_parallel_mode=@old_parallel_mode;
+SET GLOBAL slave_parallel_threads=@old_parallel_threads;
+--source include/start_slave.inc
+
+--connection master
+DROP TABLE t1, t2;
+
+--sync_slave_with_master
+--source include/rpl_end.inc
diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index 027aa5f628c..3871ddcf8ef 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -75,18 +75,18 @@ handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev)
 
   /* Do not update position if an earlier event group caused an error abort. */
   DBUG_ASSERT(qev->typ == rpl_parallel_thread::queued_event::QUEUED_POS_UPDATE);
+  rli= qev->rgi->rli;
   e= qev->entry_for_queued;
-  if (e->stop_on_error_sub_id < (uint64)ULONGLONG_MAX || e->force_abort)
+  if (e->stop_on_error_sub_id < (uint64)ULONGLONG_MAX ||
+      (e->force_abort && !rli->stop_for_until))
     return;
 
-  rli= qev->rgi->rli;
   mysql_mutex_lock(&rli->data_lock);
   cmp= strcmp(rli->group_relay_log_name, qev->event_relay_log_name);
   if (cmp < 0)
   {
     rli->group_relay_log_pos= qev->future_event_relay_log_pos;
     strmake_buf(rli->group_relay_log_name, qev->event_relay_log_name);
-    rli->notify_group_relay_log_name_update();
   } else if (cmp == 0 &&
              rli->group_relay_log_pos < qev->future_event_relay_log_pos)
     rli->group_relay_log_pos= qev->future_event_relay_log_pos;
diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index 3e1bb28f701..7215cdd4b96 100644
--- a/sql/rpl_rli.cc
+++ b/sql/rpl_rli.cc
@@ -60,6 +60,7 @@ Relay_log_info::Relay_log_info(bool is_slave_recovery)
    slave_running(MYSQL_SLAVE_NOT_RUN), until_condition(UNTIL_NONE),
    until_log_pos(0), retried_trans(0), executed_entries(0),
    sql_delay(0), sql_delay_end(0),
+   until_relay_log_names_defer(false),
    m_flags(0)
 {
   DBUG_ENTER("Relay_log_info::Relay_log_info");
@@ -499,6 +500,8 @@ void Relay_log_info::clear_until_condition()
   until_condition= Relay_log_info::UNTIL_NONE;
   until_log_name[0]= 0;
   until_log_pos= 0;
+  until_relay_log_names_defer= false;
+
   DBUG_VOID_RETURN;
 }
 
@@ -989,7 +992,6 @@ void Relay_log_info::inc_group_relay_log_pos(ulonglong log_pos,
     {
       group_relay_log_pos= rgi->future_event_relay_log_pos;
       strmake_buf(group_relay_log_name, rgi->event_relay_log_name);
-      notify_group_relay_log_name_update();
     } else if (cmp == 0 && group_relay_log_pos < rgi->future_event_relay_log_pos)
       group_relay_log_pos= rgi->future_event_relay_log_pos;
 
@@ -1279,29 +1281,78 @@ err:
      autoincrement or if we have transactions).
 
      Should be called ONLY if until_condition != UNTIL_NONE !
+
+     In the parallel execution mode and UNTIL_MASTER_POS the file name is
+     presented by future_event_master_log_name which may be ahead of
+     group_master_log_name. Log_event::log_pos does relate to it nevertheless
+     so the pair comprises a correct binlog coordinate.
+     Internal group events and events that have zero log_pos also
+     produce the zero for the local log_pos which may not lead to the
+     function falsely return true.
+     In UNTIL_RELAY_POS the original caching and notification are simplified
+     to straightforward files comparison when the current event can't be
+     a part of an event group.
+
    RETURN VALUE
      true - condition met or error happened (condition seems to have
             bad log file name)
      false - condition not met
 */
 
-bool Relay_log_info::is_until_satisfied(my_off_t master_beg_pos)
+bool Relay_log_info::is_until_satisfied(Log_event *ev)
 {
   const char *log_name;
   ulonglong log_pos;
+  /* Prevents stopping within transaction; needed solely for Relay UNTIL. */
+  bool in_trans= false;
+
   DBUG_ENTER("Relay_log_info::is_until_satisfied");
 
   if (until_condition == UNTIL_MASTER_POS)
   {
     log_name= (mi->using_parallel() ? future_event_master_log_name
                                     : group_master_log_name);
-    log_pos= master_beg_pos;
+    log_pos= (get_flag(Relay_log_info::IN_TRANSACTION) || !ev || !ev->log_pos) ?
+      (mi->using_parallel() ? 0 : group_master_log_pos) :
+      ev->log_pos - ev->data_written;
   }
   else
   {
     DBUG_ASSERT(until_condition == UNTIL_RELAY_POS);
-    log_name= group_relay_log_name;
-    log_pos= group_relay_log_pos;
+    if (!mi->using_parallel())
+    {
+      log_name= group_relay_log_name;
+      log_pos= group_relay_log_pos;
+    }
+    else
+    {
+      log_name= event_relay_log_name;
+      log_pos=  event_relay_log_pos;
+      in_trans= get_flag(Relay_log_info::IN_TRANSACTION);
+      /*
+        until_log_names_cmp_result is set to UNKNOWN either
+        -  by a non-group event *and* only when it is in the middle of a group
+        -  or by a group event when the preceding group made the above
+           non-group event to defer the resetting.
+      */
+      if ((ev && !Log_event::is_group_event(ev->get_type_code())))
+      {
+        if (in_trans)
+        {
+          until_relay_log_names_defer= true;
+        }
+        else
+        {
+          until_log_names_cmp_result= UNTIL_LOG_NAMES_CMP_UNKNOWN;
+          until_relay_log_names_defer= false;
+        }
+      }
+      else if (!in_trans && until_relay_log_names_defer)
+      {
+        until_log_names_cmp_result= UNTIL_LOG_NAMES_CMP_UNKNOWN;
+        until_relay_log_names_defer= false;
+      }
+    }
   }
 
   DBUG_PRINT("info", ("group_master_log_name='%s', group_master_log_pos=%llu",
@@ -1355,8 +1406,8 @@ bool Relay_log_info::is_until_satisfied(my_off_t master_beg_pos)
   }
 
   DBUG_RETURN(((until_log_names_cmp_result == UNTIL_LOG_NAMES_CMP_EQUAL &&
-           log_pos >= until_log_pos) ||
-          until_log_names_cmp_result == UNTIL_LOG_NAMES_CMP_GREATER));
+                (log_pos >= until_log_pos && !in_trans)) ||
+               until_log_names_cmp_result == UNTIL_LOG_NAMES_CMP_GREATER));
 }
 
 
diff --git a/sql/rpl_rli.h b/sql/rpl_rli.h
index 4ec4821b67d..2bc0a80268a 100644
--- a/sql/rpl_rli.h
+++ b/sql/rpl_rli.h
@@ -219,7 +219,7 @@ public:
   */
   char future_event_master_log_name[FN_REFLEN];
 
-  /* 
+  /*
      Original log name and position of the group we're currently executing
      (whose coordinates are group_relay_log_name/pos in the relay log)
      in the master's binlog. These concern the *group*, because in the master's
@@ -419,7 +419,7 @@ public:
   void close_temporary_tables();
 
   /* Check if UNTIL condition is satisfied. See slave.cc for more. */
-  bool is_until_satisfied(my_off_t);
+  bool is_until_satisfied(Log_event *ev);
   inline ulonglong until_pos()
   {
     DBUG_ASSERT(until_condition == UNTIL_MASTER_POS ||
@@ -427,7 +427,13 @@ public:
     return ((until_condition == UNTIL_MASTER_POS) ? group_master_log_pos :
 	    group_relay_log_pos);
   }
-
+  inline char *until_name()
+  {
+    DBUG_ASSERT(until_condition == UNTIL_MASTER_POS ||
+                until_condition == UNTIL_RELAY_POS);
+    return ((until_condition == UNTIL_MASTER_POS) ? group_master_log_name :
+	    group_relay_log_name);
+  }
   /**
     Helper function to do after statement completion.
 
@@ -564,6 +570,15 @@ private:
     relay_log.info had 4 lines. Now it has 5 lines.
   */
   static const int LINES_IN_RELAY_LOG_INFO_WITH_DELAY= 5;
+  /*
+    Hint for when to stop event distribution by sql driver thread.
+    The flag is set ON by a non-group event when this event is in the middle
+    of a group (e.g a transaction group) so it's too early
+    to refresh the current-relay-log vs until-log cached comparison result.
+    And it is checked and to decide whether it's a right time to do so
+    when the being processed group has been fully scheduled.
+  */
+  bool until_relay_log_names_defer;
 
   /*
     Holds the state of the data in the relay log.
diff --git a/sql/slave.cc b/sql/slave.cc
index eb95afd140b..1bf83aa9652 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -3921,12 +3921,8 @@ static int exec_relay_log_event(THD* thd, Relay_log_info* rli,
          rli->until_condition == Relay_log_info::UNTIL_RELAY_POS) &&
         (ev->server_id != global_system_variables.server_id ||
          rli->replicate_same_server_id) &&
-         rli->is_until_satisfied((rli->get_flag(Relay_log_info::IN_TRANSACTION) || !ev->log_pos)
-                                  ? rli->group_master_log_pos
-                                  : ev->log_pos - ev->data_written))
+        rli->is_until_satisfied(ev))
     {
-      sql_print_information("Slave SQL thread stopped because it reached its"
-                            " UNTIL position %llu", rli->until_pos());
       /*
         Setting abort_slave flag because we do not want additional
         message about error in query execution to be printed.
@@ -5136,10 +5132,14 @@ pthread_handler_t handle_slave_sql(void *arg)
   }
   if ((rli->until_condition == Relay_log_info::UNTIL_MASTER_POS ||
        rli->until_condition == Relay_log_info::UNTIL_RELAY_POS) &&
-      rli->is_until_satisfied(rli->group_master_log_pos))
+      rli->is_until_satisfied(NULL))
   {
     sql_print_information("Slave SQL thread stopped because it reached its"
-                          " UNTIL position %llu", rli->until_pos());
+                          " UNTIL position %llu in %s %s file",
+                          rli->until_pos(), rli->until_name(),
+                          rli->until_condition ==
+                          Relay_log_info::UNTIL_MASTER_POS ?
+                          "binlog" : "relaylog");
     mysql_mutex_unlock(&rli->data_lock);
     goto err;
   }
@@ -5205,7 +5205,24 @@ pthread_handler_t handle_slave_sql(void *arg)
  err:
   if (mi->using_parallel())
     rli->parallel.wait_for_done(thd, rli);
+  /* Gtid_list_log_event::do_apply_event has already reported the GTID until */
+  if (rli->stop_for_until && rli->until_condition != Relay_log_info::UNTIL_GTID)
+  {
+    if (global_system_variables.log_warnings > 2)
+      sql_print_information("Slave SQL thread UNTIL stop was requested at position "
+                            "%llu in %s %s file",
+                            rli->until_log_pos, rli->until_log_name,
+                            rli->until_condition ==
+                            Relay_log_info::UNTIL_MASTER_POS ?
+                            "binlog" : "relaylog");
+    sql_print_information("Slave SQL thread stopped because it reached its"
+                          " UNTIL position %llu in %s %s file",
+                          rli->until_pos(), rli->until_name(),
+                          rli->until_condition ==
+                          Relay_log_info::UNTIL_MASTER_POS ?
+                          "binlog" : "relaylog");
 
+  };
   /* Thread stopped. Print the current replication position to the log */
   {
     StringBuffer<100> tmp;