Merge of MDEV-4984, MDEV-4726, and MDEV-5636 into 10.0-base.

    MDEV-4984: Implement MASTER_GTID_WAIT() and @@LAST_GTID.
    MDEV-4726: Race in mysql-test/suite/rpl/t/rpl_gtid_stop_start.test
    MDEV-5636: Deadlock in RESET MASTER

18 files changed, 808 insertions, 48 deletions

diff --git a/sql/item_create.cc b/sql/item_create.cc
index 60eabe67c83..c158816bf32 100644
--- a/sql/item_create.cc
+++ b/sql/item_create.cc
@@ -1783,6 +1783,19 @@ protected:
 };
 
 
+class Create_func_master_gtid_wait : public Create_native_func
+{
+public:
+  virtual Item *create_native(THD *thd, LEX_STRING name, List<Item> *item_list);
+
+  static Create_func_master_gtid_wait s_singleton;
+
+protected:
+  Create_func_master_gtid_wait() {}
+  virtual ~Create_func_master_gtid_wait() {}
+};
+
+
 class Create_func_md5 : public Create_func_arg1
 {
 public:
@@ -4590,6 +4603,47 @@ Create_func_master_pos_wait::create_native(THD *thd, LEX_STRING name,
 }
 
 
+Create_func_master_gtid_wait Create_func_master_gtid_wait::s_singleton;
+
+Item*
+Create_func_master_gtid_wait::create_native(THD *thd, LEX_STRING name,
+                                            List<Item> *item_list)
+{
+  Item *func= NULL;
+  int arg_count= 0;
+
+  thd->lex->set_stmt_unsafe(LEX::BINLOG_STMT_UNSAFE_SYSTEM_FUNCTION);
+
+  if (item_list != NULL)
+    arg_count= item_list->elements;
+
+  if (arg_count < 1 || arg_count > 2)
+  {
+    my_error(ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT, MYF(0), name.str);
+    return func;
+  }
+
+  thd->lex->safe_to_cache_query= 0;
+
+  Item *param_1= item_list->pop();
+  switch (arg_count) {
+  case 1:
+  {
+    func= new (thd->mem_root) Item_master_gtid_wait(param_1);
+    break;
+  }
+  case 2:
+  {
+    Item *param_2= item_list->pop();
+    func= new (thd->mem_root) Item_master_gtid_wait(param_1, param_2);
+    break;
+  }
+  }
+
+  return func;
+}
+
+
 Create_func_md5 Create_func_md5::s_singleton;
 
 Item*
@@ -5536,6 +5590,7 @@ static Native_func_registry func_array[] =
   { { C_STRING_WITH_LEN("MAKEDATE") }, BUILDER(Create_func_makedate)},
   { { C_STRING_WITH_LEN("MAKETIME") }, BUILDER(Create_func_maketime)},
   { { C_STRING_WITH_LEN("MAKE_SET") }, BUILDER(Create_func_make_set)},
+  { { C_STRING_WITH_LEN("MASTER_GTID_WAIT") }, BUILDER(Create_func_master_gtid_wait)},
   { { C_STRING_WITH_LEN("MASTER_POS_WAIT") }, BUILDER(Create_func_master_pos_wait)},
   { { C_STRING_WITH_LEN("MBRCONTAINS") }, GEOM_BUILDER(Create_func_mbr_contains)},
   { { C_STRING_WITH_LEN("MBRDISJOINT") }, GEOM_BUILDER(Create_func_mbr_disjoint)},
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 2c6e195075a..df7ccea3caf 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -3991,6 +3991,34 @@ err:
 }
 
 
+longlong Item_master_gtid_wait::val_int()
+{
+  DBUG_ASSERT(fixed == 1);
+  longlong result= 0;
+
+  if (args[0]->null_value)
+  {
+    null_value= 1;
+    return 0;
+  }
+
+  null_value=0;
+#ifdef HAVE_REPLICATION
+  THD* thd= current_thd;
+  longlong timeout_us;
+  String *gtid_pos = args[0]->val_str(&value);
+
+  if (arg_count==2 && !args[1]->null_value)
+    timeout_us= (longlong)(1e6*args[1]->val_real());
+  else
+    timeout_us= (longlong)-1;
+
+  result= rpl_global_gtid_waiting.wait_for_pos(thd, gtid_pos, timeout_us);
+#endif
+  return result;
+}
+
+
 /**
   Enables a session to wait on a condition until a timeout or a network
   disconnect occurs.
diff --git a/sql/item_func.h b/sql/item_func.h
index 384a6b535df..2e3f352e377 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -1642,6 +1642,22 @@ public:
 };
 
 
+class Item_master_gtid_wait :public Item_int_func
+{
+  String value;
+public:
+  Item_master_gtid_wait(Item *a) :Item_int_func(a) {}
+  Item_master_gtid_wait(Item *a,Item *b) :Item_int_func(a,b) {}
+  longlong val_int();
+  const char *func_name() const { return "master_gtid_wait"; }
+  void fix_length_and_dec() { max_length=10+1+10+1+20+1; maybe_null=0;}
+  bool check_vcol_func_processor(uchar *int_arg) 
+  {
+    return trace_unsupported_by_check_vcol_func_processor(func_name());
+  }
+};
+
+
 /* Handling of user definable variables */
 
 class user_var_entry;
diff --git a/sql/log.cc b/sql/log.cc
index fbb73acf5d1..6fead95a4b1 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -2933,7 +2933,7 @@ const char *MYSQL_LOG::generate_name(const char *log_name,
 
 
 MYSQL_BIN_LOG::MYSQL_BIN_LOG(uint *sync_period)
-  :reset_master_pending(false),
+  :reset_master_pending(false), mark_xid_done_waiting(0),
    bytes_written(0), file_id(1), open_count(1),
    group_commit_queue(0), group_commit_queue_busy(FALSE),
    num_commits(0), num_group_commits(0),
@@ -3749,22 +3749,11 @@ bool MYSQL_BIN_LOG::reset_logs(THD* thd, bool create_new_log,
   const char* save_name;
   DBUG_ENTER("reset_logs");
 
-  if (thd)
-    ha_reset_logs(thd);
-  /*
-    We need to get both locks to be sure that no one is trying to
-    write to the index log file.
-  */
-  mysql_mutex_lock(&LOCK_log);
-  mysql_mutex_lock(&LOCK_index);
-
   if (!is_relay_log)
   {
     if (init_state && !is_empty_state())
     {
       my_error(ER_BINLOG_MUST_BE_EMPTY, MYF(0));
-      mysql_mutex_unlock(&LOCK_index);
-      mysql_mutex_unlock(&LOCK_log);
       DBUG_RETURN(1);
     }
 
@@ -3773,11 +3762,29 @@ bool MYSQL_BIN_LOG::reset_logs(THD* thd, bool create_new_log,
       This ensures that a binlog checkpoint will not try to write binlog
       checkpoint events, which would be useless (as we are deleting the binlog
       anyway) and could deadlock, as we are holding LOCK_log.
+
+      Wait for any mark_xid_done() calls that might be already running to
+      complete (mark_xid_done_waiting counter to drop to zero); we need to
+      do this before we take the LOCK_log to not deadlock.
     */
     mysql_mutex_lock(&LOCK_xid_list);
     reset_master_pending= true;
+    while (mark_xid_done_waiting > 0)
+      mysql_cond_wait(&COND_xid_list, &LOCK_xid_list);
     mysql_mutex_unlock(&LOCK_xid_list);
+  }
 
+  if (thd)
+    ha_reset_logs(thd);
+  /*
+    We need to get both locks to be sure that no one is trying to
+    write to the index log file.
+  */
+  mysql_mutex_lock(&LOCK_log);
+  mysql_mutex_lock(&LOCK_index);
+
+  if (!is_relay_log)
+  {
     /*
       We are going to nuke all binary log files.
       Without binlog, we cannot XA recover prepared-but-not-committed
@@ -5446,6 +5453,7 @@ MYSQL_BIN_LOG::write_gtid_event(THD *thd, bool standalone,
   }
   if (err)
     return true;
+  thd->last_commit_gtid= gtid;
 
   Gtid_log_event gtid_event(thd, seq_no, domain_id, standalone,
                             LOG_EVENT_SUPPRESS_USE_F, is_transactional,
@@ -8833,9 +8841,13 @@ TC_LOG_BINLOG::mark_xid_done(ulong binlog_id, bool write_checkpoint)
     locks in the opposite order.
   */
 
+  ++mark_xid_done_waiting;
   mysql_mutex_unlock(&LOCK_xid_list);
   mysql_mutex_lock(&LOCK_log);
   mysql_mutex_lock(&LOCK_xid_list);
+  --mark_xid_done_waiting;
+  if (unlikely(reset_master_pending))
+    mysql_cond_signal(&COND_xid_list);
   /* We need to reload current_binlog_id due to release/re-take of lock. */
   current= current_binlog_id;
 
diff --git a/sql/log.h b/sql/log.h
index 45381152d97..4249246277f 100644
--- a/sql/log.h
+++ b/sql/log.h
@@ -471,6 +471,7 @@ class MYSQL_BIN_LOG: public TC_LOG, private MYSQL_LOG
     checkpoint arrives - when all have arrived, RESET MASTER will complete.
   */
   bool reset_master_pending;
+  ulong mark_xid_done_waiting;
 
   /* LOCK_log and LOCK_index are inited by init_pthread_objects() */
   mysql_mutex_t LOCK_index;
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 923b8db779e..d95d856c18f 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -780,6 +780,7 @@ PSI_mutex_key key_LOCK_stats,
   key_LOCK_global_user_client_stats, key_LOCK_global_table_stats,
   key_LOCK_global_index_stats,
   key_LOCK_wakeup_ready, key_LOCK_wait_commit;
+PSI_mutex_key key_LOCK_gtid_waiting;
 
 PSI_mutex_key key_LOCK_prepare_ordered, key_LOCK_commit_ordered;
 
@@ -825,6 +826,7 @@ static PSI_mutex_info all_server_mutexes[]=
   { &key_LOCK_global_index_stats, "LOCK_global_index_stats", PSI_FLAG_GLOBAL},
   { &key_LOCK_wakeup_ready, "THD::LOCK_wakeup_ready", 0},
   { &key_LOCK_wait_commit, "wait_for_commit::LOCK_wait_commit", 0},
+  { &key_LOCK_gtid_waiting, "gtid_waiting::LOCK_gtid_waiting", 0},
   { &key_LOCK_thd_data, "THD::LOCK_thd_data", 0},
   { &key_LOCK_user_conn, "LOCK_user_conn", PSI_FLAG_GLOBAL},
   { &key_LOCK_uuid_short_generator, "LOCK_uuid_short_generator", PSI_FLAG_GLOBAL},
@@ -895,6 +897,7 @@ PSI_cond_key key_RELAYLOG_COND_queue_busy;
 PSI_cond_key key_TC_LOG_MMAP_COND_queue_busy;
 PSI_cond_key key_COND_rpl_thread, key_COND_rpl_thread_pool,
   key_COND_parallel_entry, key_COND_prepare_ordered;
+PSI_cond_key key_COND_wait_gtid;
 
 static PSI_cond_info all_server_conds[]=
 {
@@ -940,7 +943,8 @@ static PSI_cond_info all_server_conds[]=
   { &key_COND_rpl_thread, "COND_rpl_thread", 0},
   { &key_COND_rpl_thread_pool, "COND_rpl_thread_pool", 0},
   { &key_COND_parallel_entry, "COND_parallel_entry", 0},
-  { &key_COND_prepare_ordered, "COND_prepare_ordered", 0}
+  { &key_COND_prepare_ordered, "COND_prepare_ordered", 0},
+  { &key_COND_wait_gtid, "COND_wait_gtid", 0}
 };
 
 PSI_thread_key key_thread_bootstrap, key_thread_delayed_insert,
@@ -1821,6 +1825,7 @@ static void mysqld_exit(int exit_code)
     but if a kill -15 signal was sent, the signal thread did
     spawn the kill_server_thread thread, which is running concurrently.
   */
+  rpl_deinit_gtid_waiting();
   rpl_deinit_gtid_slave_state();
   wait_for_signal_thread_to_end();
   mysql_audit_finalize();
@@ -4202,6 +4207,7 @@ static int init_thread_environment()
 
 #ifdef HAVE_REPLICATION
   rpl_init_gtid_slave_state();
+  rpl_init_gtid_waiting();
 #endif
 
   DBUG_RETURN(0);
diff --git a/sql/mysqld.h b/sql/mysqld.h
index 2e10b0caeb5..4fdd34fd8be 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -256,6 +256,7 @@ extern PSI_mutex_key key_LOCK_slave_state, key_LOCK_binlog_state,
 extern PSI_mutex_key key_LOCK_stats,
   key_LOCK_global_user_client_stats, key_LOCK_global_table_stats,
   key_LOCK_global_index_stats, key_LOCK_wakeup_ready, key_LOCK_wait_commit;
+extern PSI_mutex_key key_LOCK_gtid_waiting;
 
 extern PSI_rwlock_key key_rwlock_LOCK_grant, key_rwlock_LOCK_logger,
   key_rwlock_LOCK_sys_init_connect, key_rwlock_LOCK_sys_init_slave,
@@ -285,6 +286,7 @@ extern PSI_cond_key key_RELAYLOG_COND_queue_busy;
 extern PSI_cond_key key_TC_LOG_MMAP_COND_queue_busy;
 extern PSI_cond_key key_COND_rpl_thread, key_COND_rpl_thread_pool,
   key_COND_parallel_entry;
+extern PSI_cond_key key_COND_wait_gtid;
 
 extern PSI_thread_key key_thread_bootstrap, key_thread_delayed_insert,
   key_thread_handle_manager, key_thread_kill_server, key_thread_main,
diff --git a/sql/rpl_gtid.cc b/sql/rpl_gtid.cc
index 3f79a0cb528..d7923ed9130 100644
--- a/sql/rpl_gtid.cc
+++ b/sql/rpl_gtid.cc
@@ -43,9 +43,9 @@ rpl_slave_state::update_state_hash(uint64 sub_id, rpl_gtid *gtid)
     there will not be an attempt to delete the corresponding table row before
     it is even committed.
   */
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
   err= update(gtid->domain_id, gtid->server_id, sub_id, gtid->seq_no);
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
   if (err)
   {
     sql_print_warning("Slave: Out of memory during slave state maintenance. "
@@ -82,11 +82,20 @@ rpl_slave_state::record_and_update_gtid(THD *thd, rpl_group_info *rgi)
 }
 
 
+static void
+rpl_slave_state_free_element(void *arg)
+{
+  struct rpl_slave_state::element *elem= (struct rpl_slave_state::element *)arg;
+  mysql_cond_destroy(&elem->COND_wait_gtid);
+  my_free(elem);
+}
+
+
 rpl_slave_state::rpl_slave_state()
   : last_sub_id(0), inited(false), loaded(false)
 {
   my_hash_init(&hash, &my_charset_bin, 32, offsetof(element, domain_id),
-               sizeof(uint32), NULL, my_free, HASH_UNIQUE);
+               sizeof(uint32), NULL, rpl_slave_state_free_element, HASH_UNIQUE);
 }
 
 
@@ -146,6 +155,21 @@ rpl_slave_state::update(uint32 domain_id, uint32 server_id, uint64 sub_id,
   if (!(elem= get_element(domain_id)))
     return 1;
 
+  if (seq_no > elem->highest_seq_no)
+    elem->highest_seq_no= seq_no;
+  if (elem->gtid_waiter && elem->min_wait_seq_no <= seq_no)
+  {
+    /*
+      Someone was waiting in MASTER_GTID_WAIT() for this GTID to appear.
+      Signal (and remove) them. The waiter will handle all the processing
+      of all pending MASTER_GTID_WAIT(), so we do not slow down the
+      replication SQL thread.
+    */
+    mysql_mutex_assert_owner(&LOCK_slave_state);
+    elem->gtid_waiter= NULL;
+    mysql_cond_broadcast(&elem->COND_wait_gtid);
+  }
+
   if (!(list_elem= (list_element *)my_malloc(sizeof(*list_elem), MYF(MY_WME))))
     return 1;
   list_elem->server_id= server_id;
@@ -173,6 +197,9 @@ rpl_slave_state::get_element(uint32 domain_id)
     return NULL;
   elem->list= NULL;
   elem->domain_id= domain_id;
+  elem->highest_seq_no= 0;
+  elem->gtid_waiter= NULL;
+  mysql_cond_init(key_COND_wait_gtid, &elem->COND_wait_gtid, 0);
   if (my_hash_insert(&hash, (uchar *)elem))
   {
     my_free(elem);
@@ -378,10 +405,10 @@ rpl_slave_state::record_gtid(THD *thd, const rpl_gtid *gtid, uint64 sub_id,
     goto end;
   }
 
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
   if ((elem= get_element(gtid->domain_id)) == NULL)
   {
-    unlock();
+    mysql_mutex_unlock(&LOCK_slave_state);
     my_error(ER_OUT_OF_RESOURCES, MYF(0));
     err= 1;
     goto end;
@@ -410,7 +437,7 @@ rpl_slave_state::record_gtid(THD *thd, const rpl_gtid *gtid, uint64 sub_id,
     cur->next= NULL;
     elem->list= cur;
   }
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
 
   if (!elist)
     goto end;
@@ -470,9 +497,9 @@ end:
       */
       if (elist)
       {
-        lock();
+        mysql_mutex_lock(&LOCK_slave_state);
         put_back_list(gtid->domain_id, elist);
-        unlock();
+        mysql_mutex_unlock(&LOCK_slave_state);
       }
 
       ha_rollback_trans(thd, FALSE);
@@ -499,9 +526,9 @@ rpl_slave_state::next_sub_id(uint32 domain_id)
 {
   uint64 sub_id= 0;
 
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
   sub_id= ++last_sub_id;
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
 
   return sub_id;
 }
@@ -541,7 +568,7 @@ rpl_slave_state::iterate(int (*cb)(rpl_gtid *, void *), void *data,
         my_hash_insert(&gtid_hash, (uchar *)(&extra_gtids[i])))
       goto err;
 
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
 
   for (i= 0; i < hash.records; ++i)
   {
@@ -576,19 +603,19 @@ rpl_slave_state::iterate(int (*cb)(rpl_gtid *, void *), void *data,
         memcpy(&best_gtid, gtid, sizeof(best_gtid));
       if (my_hash_delete(&gtid_hash, rec))
       {
-        unlock();
+        mysql_mutex_unlock(&LOCK_slave_state);
         goto err;
       }
     }
 
     if ((res= (*cb)(&best_gtid, data)))
     {
-      unlock();
+      mysql_mutex_unlock(&LOCK_slave_state);
       goto err;
     }
   }
 
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
 
   /* Also add any remaining extra domain_ids. */
   for (i= 0; i < gtid_hash.records; ++i)
@@ -659,11 +686,11 @@ rpl_slave_state::domain_to_gtid(uint32 domain_id, rpl_gtid *out_gtid)
   list_element *list;
   uint64 best_sub_id;
 
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
   elem= (element *)my_hash_search(&hash, (const uchar *)&domain_id, 0);
   if (!elem || !(list= elem->list))
   {
-    unlock();
+    mysql_mutex_unlock(&LOCK_slave_state);
     return false;
   }
 
@@ -681,7 +708,7 @@ rpl_slave_state::domain_to_gtid(uint32 domain_id, rpl_gtid *out_gtid)
     out_gtid->seq_no= list->seq_no;
   }
 
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
   return true;
 }
 
@@ -811,7 +838,7 @@ rpl_slave_state::is_empty()
   uint32 i;
   bool result= true;
 
-  lock();
+  mysql_mutex_lock(&LOCK_slave_state);
   for (i= 0; i < hash.records; ++i)
   {
     element *e= (element *)my_hash_element(&hash, i);
@@ -821,7 +848,7 @@ rpl_slave_state::is_empty()
       break;
     }
   }
-  unlock();
+  mysql_mutex_unlock(&LOCK_slave_state);
 
   return result;
 }
@@ -1647,3 +1674,445 @@ slave_connection_state::get_gtid_list(rpl_gtid *gtid_list, uint32 list_size)
 
   return 0;
 }
+
+
+/*
+  Execute a MASTER_GTID_WAIT().
+  The position to wait for is in gtid_str in string form.
+  The timeout in microseconds is in timeout_us, zero means no timeout.
+
+  Returns:
+   1 for error.
+   0 for wait completed.
+  -1 for wait timed out.
+*/
+int
+gtid_waiting::wait_for_pos(THD *thd, String *gtid_str, longlong timeout_us)
+{
+  int err;
+  rpl_gtid *wait_pos;
+  uint32 count, i;
+  struct timespec wait_until, *wait_until_ptr;
+
+  /* Wait for the empty position returns immediately. */
+  if (gtid_str->length() == 0)
+    return 0;
+
+  if (!(wait_pos= gtid_parse_string_to_list(gtid_str->ptr(), gtid_str->length(),
+                                            &count)))
+  {
+    my_error(ER_INCORRECT_GTID_STATE, MYF(0));
+    return 1;
+  }
+
+  if (timeout_us >= 0)
+  {
+    set_timespec_nsec(wait_until, (ulonglong)1000*timeout_us);
+    wait_until_ptr= &wait_until;
+  }
+  else
+    wait_until_ptr= NULL;
+  err= 0;
+  for (i= 0; i < count; ++i)
+  {
+    if ((err= wait_for_gtid(thd, &wait_pos[i], wait_until_ptr)))
+      break;
+  }
+  my_free(wait_pos);
+  return err;
+}
+
+
+void
+gtid_waiting::promote_new_waiter(gtid_waiting::hash_element *he)
+{
+  queue_element *qe;
+
+  mysql_mutex_assert_owner(&LOCK_gtid_waiting);
+  if (queue_empty(&he->queue))
+    return;
+  qe= (queue_element *)queue_top(&he->queue);
+  qe->do_small_wait= true;
+  mysql_cond_signal(&qe->thd->COND_wakeup_ready);
+}
+
+void
+gtid_waiting::process_wait_hash(uint64 wakeup_seq_no,
+                                gtid_waiting::hash_element *he)
+{
+  mysql_mutex_assert_owner(&LOCK_gtid_waiting);
+
+  for (;;)
+  {
+    queue_element *qe;
+
+    if (queue_empty(&he->queue))
+      break;
+    qe= (queue_element *)queue_top(&he->queue);
+    if (qe->wait_seq_no > wakeup_seq_no)
+      break;
+    DBUG_ASSERT(!qe->done);
+    queue_remove_top(&he->queue);
+    qe->done= true;;
+    mysql_cond_signal(&qe->thd->COND_wakeup_ready);
+  }
+}
+
+
+/*
+  Execute a MASTER_GTID_WAIT() for one specific domain.
+
+  The implementation is optimised primarily for (1) minimal performance impact
+  on the slave replication threads, and secondarily for (2) quick performance
+  of MASTER_GTID_WAIT() on a single GTID, which can be useful for consistent
+  read to clients in an async replication read-scaleout scenario.
+
+  To achieve (1), we have a "small" wait and a "large" wait. The small wait
+  contends with the replication threads on the lock on the gtid_slave_pos, so
+  only minimal processing is done under that lock, and only a single waiter at
+  a time does the small wait.
+
+  If there is already a small waiter, a new thread will either replace the
+  small waiter (if it needs to wait for an earlier sequence number), or
+  instead do a "large" wait.
+
+  Once awoken on the small wait, the waiting thread releases the lock shared
+  with the SQL threads quickly, and then processes all waiters currently doing
+  the large wait using a different lock that does not impact replication.
+
+  This way, the SQL threads only need to do a single check + possibly a
+  pthread_cond_signal() when updating the gtid_slave_state, and the time that
+  non-SQL threads contend for the lock on gtid_slave_state is minimized.
+
+  There is always at least one thread that has the responsibility to ensure
+  that there is a small waiter; this thread has queue_element::do_small_wait
+  set to true. This thread will do the small wait until it is done, at which
+  point it will make sure to pass on the responsibility to another thread.
+  Normally only one thread has do_small_wait==true, but it can occasionally
+  happen that there is more than one, when threads race one another for the
+  lock on the small wait (this results in slightly increased activity on the
+  small lock but is otherwise harmless).
+
+  Returns:
+     0  Wait completed normally
+    -1  Wait completed due to timeout
+     1  An error (my_error() will have been called to set the error in the da)
+*/
+int
+gtid_waiting::wait_for_gtid(THD *thd, rpl_gtid *wait_gtid,
+                            struct timespec *wait_until)
+{
+  bool timed_out= false;
+#ifdef HAVE_REPLICATION
+  queue_element elem;
+  uint32 domain_id= wait_gtid->domain_id;
+  uint64 seq_no= wait_gtid->seq_no;
+  hash_element *he;
+  rpl_slave_state::element *slave_state_elem= NULL;
+  const char *old_msg= NULL;
+  bool did_enter_cond= false;
+
+  elem.wait_seq_no= seq_no;
+  elem.thd= thd;
+  elem.done= false;
+
+  mysql_mutex_lock(&LOCK_gtid_waiting);
+  if (!(he= get_entry(wait_gtid->domain_id)))
+  {
+    mysql_mutex_unlock(&LOCK_gtid_waiting);
+    return 1;
+  }
+  /*
+    If there is already another waiter with seq_no no larger than our own,
+    we are sure that there is already a small waiter that will wake us up
+    (or later pass the small wait responsibility to us). So in this case, we
+    do not need to touch the small wait lock at all.
+  */
+  elem.do_small_wait=
+    (queue_empty(&he->queue) ||
+     ((queue_element *)queue_top(&he->queue))->wait_seq_no > seq_no);
+
+  if (register_in_wait_queue(thd, wait_gtid, he, &elem))
+  {
+    mysql_mutex_unlock(&LOCK_gtid_waiting);
+    return 1;
+  }
+  /*
+    Loop, doing either the small or large wait as appropriate, until either
+    the position waited for is reached, or we get a kill or timeout.
+  */
+  for (;;)
+  {
+    mysql_mutex_assert_owner(&LOCK_gtid_waiting);
+
+    if (elem.do_small_wait)
+    {
+      uint64 wakeup_seq_no;
+      queue_element *cur_waiter;
+
+      mysql_mutex_lock(&rpl_global_gtid_slave_state.LOCK_slave_state);
+      /*
+        The elements in the gtid_slave_state_hash are never re-allocated once
+        they enter the hash, so we do not need to re-do the lookup after releasing
+        and re-aquiring the lock.
+      */
+      if (!slave_state_elem &&
+          !(slave_state_elem= rpl_global_gtid_slave_state.get_element(domain_id)))
+      {
+        mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
+        remove_from_wait_queue(he, &elem);
+        promote_new_waiter(he);
+        if (did_enter_cond)
+          thd->exit_cond(old_msg);
+        else
+          mysql_mutex_unlock(&LOCK_gtid_waiting);
+        my_error(ER_OUT_OF_RESOURCES, MYF(0));
+        return 1;
+      }
+
+      if ((wakeup_seq_no= slave_state_elem->highest_seq_no) >= seq_no)
+      {
+        /*
+          We do not have to wait. (We will be removed from the wait queue when
+          we call process_wait_hash() below.
+        */
+        mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
+      }
+      else if ((cur_waiter= slave_state_elem->gtid_waiter) &&
+               slave_state_elem->min_wait_seq_no <= seq_no)
+      {
+        /*
+          There is already a suitable small waiter, go do the large wait.
+          (Normally we would not have needed to check the small wait in this
+          case, but it can happen if we race with another thread for the small
+          lock).
+        */
+        elem.do_small_wait= false;
+        mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
+      }
+      else
+      {
+        /*
+          We have to do the small wait ourselves (stealing it from any thread
+          that might already be waiting for a later seq_no).
+        */
+        slave_state_elem->gtid_waiter= &elem;
+        slave_state_elem->min_wait_seq_no= seq_no;
+        if (cur_waiter)
+        {
+          /* We stole the wait, so wake up the old waiting thread. */
+          mysql_cond_signal(&slave_state_elem->COND_wait_gtid);
+        }
+
+        /* Release the large lock, and do the small wait. */
+        if (did_enter_cond)
+        {
+          thd->exit_cond(old_msg);
+          did_enter_cond= false;
+        }
+        else
+          mysql_mutex_unlock(&LOCK_gtid_waiting);
+        old_msg=
+          thd->enter_cond(&slave_state_elem->COND_wait_gtid,
+                          &rpl_global_gtid_slave_state.LOCK_slave_state,
+                          "Waiting in MASTER_GTID_WAIT() (primary waiter)");
+        do
+        {
+          if (thd->check_killed())
+            break;
+          else if (wait_until)
+          {
+            int err=
+              mysql_cond_timedwait(&slave_state_elem->COND_wait_gtid,
+                                   &rpl_global_gtid_slave_state.LOCK_slave_state,
+                                   wait_until);
+            if (err == ETIMEDOUT || err == ETIME)
+            {
+              timed_out= true;
+              break;
+            }
+          }
+          else
+            mysql_cond_wait(&slave_state_elem->COND_wait_gtid,
+                            &rpl_global_gtid_slave_state.LOCK_slave_state);
+        } while (slave_state_elem->gtid_waiter == &elem);
+        wakeup_seq_no= slave_state_elem->highest_seq_no;
+        /*
+          If we aborted due to timeout or kill, remove us as waiter.
+
+          If we were replaced by another waiter with a smaller seq_no, then we
+          no longer have responsibility for the small wait.
+        */
+        if ((cur_waiter= slave_state_elem->gtid_waiter))
+        {
+          if (cur_waiter == &elem)
+            slave_state_elem->gtid_waiter= NULL;
+          else if (slave_state_elem->min_wait_seq_no <= seq_no)
+            elem.do_small_wait= false;
+        }
+        thd->exit_cond(old_msg);
+
+        mysql_mutex_lock(&LOCK_gtid_waiting);
+      }
+
+      /*
+        Note that hash_entry pointers do not change once allocated, so we do
+        not need to lookup `he' again after re-aquiring LOCK_gtid_waiting.
+      */
+      process_wait_hash(wakeup_seq_no, he);
+    }
+    else
+    {
+      /* Do the large wait. */
+      if (!did_enter_cond)
+      {
+        old_msg= thd->enter_cond(&thd->COND_wakeup_ready, &LOCK_gtid_waiting,
+                                 "Waiting in MASTER_GTID_WAIT()");
+        did_enter_cond= true;
+      }
+      while (!elem.done && !thd->check_killed())
+      {
+        thd_wait_begin(thd, THD_WAIT_BINLOG);
+        if (wait_until)
+        {
+          int err= mysql_cond_timedwait(&thd->COND_wakeup_ready,
+                                        &LOCK_gtid_waiting, wait_until);
+          if (err == ETIMEDOUT || err == ETIME)
+            timed_out= true;
+        }
+        else
+          mysql_cond_wait(&thd->COND_wakeup_ready, &LOCK_gtid_waiting);
+        thd_wait_end(thd);
+        if (elem.do_small_wait || timed_out)
+          break;
+      }
+    }
+
+    if ((thd->killed || timed_out) && !elem.done)
+    {
+      /* Aborted, so remove ourselves from the hash. */
+      remove_from_wait_queue(he, &elem);
+      elem.done= true;
+    }
+    if (elem.done)
+    {
+      /*
+        If our wait is done, but we have (or were passed) responsibility for
+        the small wait, then we need to pass on that task to someone else.
+      */
+      if (elem.do_small_wait)
+        promote_new_waiter(he);
+      break;
+    }
+  }
+
+  if (did_enter_cond)
+    thd->exit_cond(old_msg);
+  else
+    mysql_mutex_unlock(&LOCK_gtid_waiting);
+  if (thd->killed)
+    thd->send_kill_message();
+#endif  /* HAVE_REPLICATION */
+  return timed_out ? -1 : 0;
+}
+
+
+static void
+free_hash_element(void *p)
+{
+  gtid_waiting::hash_element *e= (gtid_waiting::hash_element *)p;
+  delete_queue(&e->queue);
+  my_free(e);
+}
+
+
+void
+gtid_waiting::init()
+{
+  my_hash_init(&hash, &my_charset_bin, 32,
+               offsetof(hash_element, domain_id), sizeof(uint32), NULL,
+               free_hash_element, HASH_UNIQUE);
+  mysql_mutex_init(key_LOCK_gtid_waiting, &LOCK_gtid_waiting, 0);
+}
+
+
+void
+gtid_waiting::destroy()
+{
+  mysql_mutex_destroy(&LOCK_gtid_waiting);
+  my_hash_free(&hash);
+}
+
+
+static int
+cmp_queue_elem(void *, uchar *a, uchar *b)
+{
+  uint64 seq_no_a= *(uint64 *)a;
+  uint64 seq_no_b= *(uint64 *)b;
+  if (seq_no_a < seq_no_b)
+    return -1;
+  else if (seq_no_a == seq_no_b)
+    return 0;
+  else
+    return 1;
+}
+
+
+gtid_waiting::hash_element *
+gtid_waiting::get_entry(uint32 domain_id)
+{
+  hash_element *e;
+
+  if ((e= (hash_element *)my_hash_search(&hash, (const uchar *)&domain_id, 0)))
+    return e;
+
+  if (!(e= (hash_element *)my_malloc(sizeof(*e), MYF(MY_WME))))
+  {
+    my_error(ER_OUTOFMEMORY, MYF(0), sizeof(*e));
+    return NULL;
+  }
+
+  if (init_queue(&e->queue, 8, offsetof(queue_element, wait_seq_no), 0,
+                 cmp_queue_elem, NULL, 1+offsetof(queue_element, queue_idx), 1))
+  {
+    my_error(ER_OUT_OF_RESOURCES, MYF(0));
+    my_free(e);
+    return NULL;
+  }
+  e->domain_id= domain_id;
+  if (my_hash_insert(&hash, (uchar *)e))
+  {
+    my_error(ER_OUT_OF_RESOURCES, MYF(0));
+    delete_queue(&e->queue);
+    my_free(e);
+    return NULL;
+  }
+  return e;
+}
+
+
+int
+gtid_waiting::register_in_wait_queue(THD *thd, rpl_gtid *wait_gtid,
+                                     gtid_waiting::hash_element *he,
+                                     gtid_waiting::queue_element *elem)
+{
+  mysql_mutex_assert_owner(&LOCK_gtid_waiting);
+
+  if (queue_insert_safe(&he->queue, (uchar *)elem))
+  {
+    my_error(ER_OUT_OF_RESOURCES, MYF(0));
+    return 1;
+  }
+
+  return 0;
+}
+
+
+void
+gtid_waiting::remove_from_wait_queue(gtid_waiting::hash_element *he,
+                                     gtid_waiting::queue_element *elem)
+{
+  mysql_mutex_assert_owner(&LOCK_gtid_waiting);
+
+  queue_remove(&he->queue, elem->queue_idx);
+}
diff --git a/sql/rpl_gtid.h b/sql/rpl_gtid.h
index b0bc54900e7..54f352661a7 100644
--- a/sql/rpl_gtid.h
+++ b/sql/rpl_gtid.h
@@ -16,6 +16,10 @@
 #ifndef RPL_GTID_H
 #define RPL_GTID_H
 
+#include "hash.h"
+#include "queues.h"
+
+
 /* Definitions for MariaDB global transaction ID (GTID). */
 
 
@@ -37,6 +41,57 @@ enum enum_gtid_skip_type {
 
 
 /*
+  Structure to keep track of threads waiting in MASTER_GTID_WAIT().
+
+  Since replication is (mostly) single-threaded, we want to minimise the
+  performance impact on that from MASTER_GTID_WAIT(). To achieve this, we
+  are careful to keep the common lock between replication threads and
+  MASTER_GTID_WAIT threads held for as short as possible. We keep only
+  a single thread waiting to be notified by the replication threads; this
+  thread then handles all the (potentially heavy) lifting of dealing with
+  all current waiting threads.
+*/
+struct gtid_waiting {
+  /* Elements in the hash, basically a priority queue for each domain. */
+  struct hash_element {
+    QUEUE queue;
+    uint32 domain_id;
+  };
+  /* A priority queue to handle waiters in one domain in seq_no order. */
+  struct queue_element {
+    uint64 wait_seq_no;
+    THD *thd;
+    int queue_idx;
+    /*
+      do_small_wait is true if we have responsibility for ensuring that there
+      is a small waiter.
+    */
+    bool do_small_wait;
+    /*
+      The flag `done' is set when the wait is completed (either due to reaching
+      the position waited for, or due to timeout or kill). The queue_element
+      is in the queue if and only if `done' is true.
+    */
+    bool done;
+  };
+
+  mysql_mutex_t LOCK_gtid_waiting;
+  HASH hash;
+
+  void init();
+  void destroy();
+  hash_element *get_entry(uint32 domain_id);
+  int wait_for_pos(THD *thd, String *gtid_str, longlong timeout_us);
+  void promote_new_waiter(gtid_waiting::hash_element *he);
+  int wait_for_gtid(THD *thd, rpl_gtid *wait_gtid, struct timespec *wait_until);
+  void process_wait_hash(uint64 wakeup_seq_no, gtid_waiting::hash_element *he);
+  int register_in_wait_queue(THD *thd, rpl_gtid *wait_gtid, hash_element *he,
+                             queue_element *elem);
+  void remove_from_wait_queue(hash_element *he, queue_element *elem);
+};
+
+
+/*
   Replication slave state.
 
   For every independent replication stream (identified by domain_id), this
@@ -61,6 +116,20 @@ struct rpl_slave_state
   {
     struct list_element *list;
     uint32 domain_id;
+    /* Highest seq_no seen so far in this domain. */
+    uint64 highest_seq_no;
+    /*
+      If this is non-NULL, then it is the waiter responsible for the small
+      wait in MASTER_GTID_WAIT().
+    */
+    gtid_waiting::queue_element *gtid_waiter;
+    /*
+      If gtid_waiter is non-NULL, then this is the seq_no that its
+      MASTER_GTID_WAIT() is waiting on. When we reach this seq_no, we need to
+      signal the waiter on COND_wait_gtid.
+    */
+    uint64 min_wait_seq_no;
+    mysql_cond_t COND_wait_gtid;
 
     list_element *grab_list() { list_element *l= list; list= NULL; return l; }
     void add(list_element *l)
@@ -99,9 +168,6 @@ struct rpl_slave_state
            bool in_statement);
   bool is_empty();
 
-  void lock() { DBUG_ASSERT(inited); mysql_mutex_lock(&LOCK_slave_state); }
-  void unlock() { DBUG_ASSERT(inited); mysql_mutex_unlock(&LOCK_slave_state); }
-
   element *get_element(uint32 domain_id);
   int put_back_list(uint32 domain_id, list_element *list);
 
@@ -204,6 +270,7 @@ struct slave_connection_state
   int get_gtid_list(rpl_gtid *gtid_list, uint32 list_size);
 };
 
+
 extern bool rpl_slave_state_tostring_helper(String *dest, const rpl_gtid *gtid,
                                             bool *first);
 extern int gtid_check_rpl_slave_state_table(TABLE *table);
diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index 7f0ec702b87..797f5681ec5 100644
--- a/sql/rpl_rli.cc
+++ b/sql/rpl_rli.cc
@@ -37,6 +37,8 @@ static int count_relay_log_space(Relay_log_info* rli);
    domain).
 */
 rpl_slave_state rpl_global_gtid_slave_state;
+/* Object used for MASTER_GTID_WAIT(). */
+gtid_waiting rpl_global_gtid_waiting;
 
 
 // Defined in slave.cc
@@ -1317,9 +1319,9 @@ rpl_load_gtid_slave_state(THD *thd)
   uint32 i;
   DBUG_ENTER("rpl_load_gtid_slave_state");
 
-  rpl_global_gtid_slave_state.lock();
+  mysql_mutex_lock(&rpl_global_gtid_slave_state.LOCK_slave_state);
   bool loaded= rpl_global_gtid_slave_state.loaded;
-  rpl_global_gtid_slave_state.unlock();
+  mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
   if (loaded)
     DBUG_RETURN(0);
 
@@ -1419,10 +1421,10 @@ rpl_load_gtid_slave_state(THD *thd)
     }
   }
 
-  rpl_global_gtid_slave_state.lock();
+  mysql_mutex_lock(&rpl_global_gtid_slave_state.LOCK_slave_state);
   if (rpl_global_gtid_slave_state.loaded)
   {
-    rpl_global_gtid_slave_state.unlock();
+    mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
     goto end;
   }
 
@@ -1434,7 +1436,7 @@ rpl_load_gtid_slave_state(THD *thd)
                                                  tmp_entry.sub_id,
                                                  tmp_entry.gtid.seq_no)))
     {
-      rpl_global_gtid_slave_state.unlock();
+      mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
       my_error(ER_OUT_OF_RESOURCES, MYF(0));
       goto end;
     }
@@ -1447,14 +1449,14 @@ rpl_load_gtid_slave_state(THD *thd)
         mysql_bin_log.bump_seq_no_counter_if_needed(entry->gtid.domain_id,
                                                     entry->gtid.seq_no))
     {
-      rpl_global_gtid_slave_state.unlock();
+      mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
       my_error(ER_OUT_OF_RESOURCES, MYF(0));
       goto end;
     }
   }
 
   rpl_global_gtid_slave_state.loaded= true;
-  rpl_global_gtid_slave_state.unlock();
+  mysql_mutex_unlock(&rpl_global_gtid_slave_state.LOCK_slave_state);
 
   err= 0;                                       /* Clear HA_ERR_END_OF_FILE */
 
diff --git a/sql/rpl_rli.h b/sql/rpl_rli.h
index 6716718d354..3f95849a926 100644
--- a/sql/rpl_rli.h
+++ b/sql/rpl_rli.h
@@ -708,6 +708,7 @@ int init_relay_log_info(Relay_log_info* rli, const char* info_fname);
 
 
 extern struct rpl_slave_state rpl_global_gtid_slave_state;
+extern gtid_waiting rpl_global_gtid_waiting;
 
 int rpl_load_gtid_slave_state(THD *thd);
 int event_group_new_gtid(rpl_group_info *rgi, Gtid_log_event *gev);
diff --git a/sql/share/errmsg-utf8.txt b/sql/share/errmsg-utf8.txt
index 0c9c84d4964..1ed2a2ba462 100644
--- a/sql/share/errmsg-utf8.txt
+++ b/sql/share/errmsg-utf8.txt
@@ -6524,7 +6524,7 @@ ER_UNTIL_REQUIRES_USING_GTID
 ER_GTID_STRICT_OUT_OF_ORDER
 	eng "An attempt was made to binlog GTID %u-%u-%llu which would create an out-of-order sequence number with existing GTID %u-%u-%llu, and gtid strict mode is enabled."
 ER_GTID_START_FROM_BINLOG_HOLE
-	eng "The binlog on the master is missing the GTID %u-%u-%llu requested by the slave (even though both a prior and a subsequent sequence number does exist), and GTID strict mode is enabled"
+	eng "The binlog on the master is missing the GTID %u-%u-%llu requested by the slave (even though a subsequent sequence number does exist), and GTID strict mode is enabled"
 ER_SLAVE_UNEXPECTED_MASTER_SWITCH
 	eng "Unexpected GTID received from master after reconnect. This normally indicates that the master server was replaced without restarting the slave threads. %s"
 ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index c446d901055..09ec7361fe3 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1267,6 +1267,7 @@ void THD::init(void)
   set_status_var_init();
   bzero((char *) &org_status_var, sizeof(org_status_var));
   start_bytes_received= 0;
+  last_commit_gtid.seq_no= 0;
 
   if (variables.sql_log_bin)
     variables.option_bits|= OPTION_BIN_LOG;
diff --git a/sql/sql_class.h b/sql/sql_class.h
index a7e3290c543..726b920edb1 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -44,6 +44,7 @@
 #include "thr_lock.h"             /* thr_lock_type, THR_LOCK_DATA,
                                      THR_LOCK_INFO */
 #include "my_apc.h"
+#include "rpl_gtid.h"
 
 class Reprepare_observer;
 class Relay_log_info;
@@ -3410,6 +3411,12 @@ private:
    */
   LEX_STRING invoker_user;
   LEX_STRING invoker_host;
+
+  /* Protect against add/delete of temporary tables in parallel replication */
+  void rgi_lock_temporary_tables();
+  void rgi_unlock_temporary_tables();
+  bool rgi_have_temporary_tables();
+public:
   /*
     Flag, mutex and condition for a thread to wait for a signal from another
     thread.
@@ -3420,12 +3427,12 @@ private:
   bool wakeup_ready;
   mysql_mutex_t LOCK_wakeup_ready;
   mysql_cond_t COND_wakeup_ready;
+  /*
+     The GTID assigned to the last commit. If no GTID was assigned to any commit
+     so far, this is indicated by last_commit_gtid.seq_no == 0.
+  */
+  rpl_gtid last_commit_gtid;
 
-  /* Protect against add/delete of temporary tables in parallel replication */
-  void rgi_lock_temporary_tables();
-  void rgi_unlock_temporary_tables();
-  bool rgi_have_temporary_tables();
-public:
   inline void lock_temporary_tables()
   {
     if (rgi_slave)
diff --git a/sql/sql_repl.cc b/sql/sql_repl.cc
index 363b53e05a6..7c4e5b1b383 100644
--- a/sql/sql_repl.cc
+++ b/sql/sql_repl.cc
@@ -3965,6 +3965,20 @@ rpl_deinit_gtid_slave_state()
 }
 
 
+void
+rpl_init_gtid_waiting()
+{
+  rpl_global_gtid_waiting.init();
+}
+
+
+void
+rpl_deinit_gtid_waiting()
+{
+  rpl_global_gtid_waiting.destroy();
+}
+
+
 /*
   Format the current GTID state as a string, for returning the value of
   @@global.gtid_slave_pos.
diff --git a/sql/sql_repl.h b/sql/sql_repl.h
index da55e3e863f..defb1b23f5b 100644
--- a/sql/sql_repl.h
+++ b/sql/sql_repl.h
@@ -70,6 +70,8 @@ void mysql_binlog_send(THD* thd, char* log_ident, my_off_t pos, ushort flags);
 extern PSI_mutex_key key_LOCK_slave_state, key_LOCK_binlog_state;
 void rpl_init_gtid_slave_state();
 void rpl_deinit_gtid_slave_state();
+void rpl_init_gtid_waiting();
+void rpl_deinit_gtid_waiting();
 int gtid_state_from_binlog_pos(const char *name, uint32 pos, String *out_str);
 int rpl_append_gtid_state(String *dest, bool use_binlog);
 int rpl_load_gtid_state(slave_connection_state *state, bool use_binlog);
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 7b0b64f9961..0495ee3e240 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -1538,6 +1538,33 @@ static Sys_var_gtid_binlog_state Sys_gtid_binlog_state(
        GLOBAL_VAR(opt_gtid_binlog_state_dummy), NO_CMD_LINE);
 
 
+static Sys_var_last_gtid Sys_last_gtid(
+       "last_gtid", "The GTID of the last commit (if binlogging was enabled), "
+       "or the empty string if none.",
+       READ_ONLY sys_var::ONLY_SESSION, NO_CMD_LINE);
+
+
+uchar *
+Sys_var_last_gtid::session_value_ptr(THD *thd, LEX_STRING *base)
+{
+  char buf[10+1+10+1+20+1];
+  String str(buf, sizeof(buf), system_charset_info);
+  char *p;
+  bool first= true;
+
+  str.length(0);
+  if ((thd->last_commit_gtid.seq_no > 0 &&
+       rpl_slave_state_tostring_helper(&str, &thd->last_commit_gtid, &first)) ||
+      !(p= thd->strmake(str.ptr(), str.length())))
+  {
+    my_error(ER_OUT_OF_RESOURCES, MYF(0));
+    return NULL;
+  }
+
+  return (uchar *)p;
+}
+
+
 static bool
 check_slave_parallel_threads(sys_var *self, THD *thd, set_var *var)
 {
diff --git a/sql/sys_vars.h b/sql/sys_vars.h
index 3cc4da32811..6a84fc5fbc2 100644
--- a/sql/sys_vars.h
+++ b/sql/sys_vars.h
@@ -2211,3 +2211,53 @@ public:
   }
   uchar *global_value_ptr(THD *thd, LEX_STRING *base);
 };
+
+
+/**
+  Class for @@session.last_gtid.
+*/
+class Sys_var_last_gtid: public sys_var
+{
+public:
+  Sys_var_last_gtid(const char *name_arg,
+          const char *comment, int flag_args, CMD_LINE getopt)
+    : sys_var(&all_sys_vars, name_arg, comment, flag_args, 0, getopt.id,
+              getopt.arg_type, SHOW_CHAR, 0, NULL, VARIABLE_NOT_IN_BINLOG,
+              NULL, NULL, NULL)
+  {
+    option.var_type= GET_STR;
+  }
+  bool do_check(THD *thd, set_var *var)
+  {
+    DBUG_ASSERT(false);
+    return true;
+  }
+  bool session_update(THD *thd, set_var *var)
+  {
+    DBUG_ASSERT(false);
+    return true;
+  }
+  bool global_update(THD *thd, set_var *var)
+  {
+    DBUG_ASSERT(false);
+    return true;
+  }
+  bool check_update_type(Item_result type) {
+    DBUG_ASSERT(false);
+    return false;
+  }
+  void session_save_default(THD *thd, set_var *var)
+  {
+    DBUG_ASSERT(false);
+  }
+  void global_save_default(THD *thd, set_var *var)
+  {
+    DBUG_ASSERT(false);
+  }
+  uchar *session_value_ptr(THD *thd, LEX_STRING *base);
+  uchar *global_value_ptr(THD *thd, LEX_STRING *base)
+  {
+    DBUG_ASSERT(false);
+    return NULL;
+  }
+};