MDEV-4984: Implement MASTER_GTID_WAIT() and @@LAST_GTID.

MASTER_GTID_WAIT() is similar to MASTER_POS_WAIT(), but works with a
GTID position rather than an old-style filename/offset.

@@LAST_GTID gives the GTID assigned to the last transaction written
into the binlog.

Together, the two can be used by applications to obtain the GTID of
an update on the master, and then do a MASTER_GTID_WAIT() for that
position on any read slave where it is important to get results that
are caught up with the master at least to the point of the update.

The implementation of MASTER_GTID_WAIT() is implemented in a way
that tries to minimise the performance impact on the SQL threads,
even in the presense of many waiters on single GTID positions (as
from @@LAST_GTID).

1 files changed, 9 insertions, 7 deletions

diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index cfa7c0f344f..8384297624c 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
@@ -1312,9 +1314,9 @@ 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);
 
@@ -1414,10 +1416,10 @@ 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;
   }
 
@@ -1429,7 +1431,7 @@ 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;
     }
@@ -1442,14 +1444,14 @@ 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 */