MDEV-7145: Delayed replication, intermediate commit.

Initial merge of delayed replication from MySQL git.

The code from the initial push into MySQL is merged, and the
associated test case passes. A number of tasks are still pending:

1. Check full test suite run for any regressions or .result file updates.

2. Extend the feature to also work for parallel replication.

3. There are some todo-comments about future refactoring left from
MySQL, these should be located and merged on top.

4. There are some later related MySQL commits, these should be checked
and merged. These include:
    e134b9362ba0b750d6ac1b444780019622d14aa5
    b38f0f7857c073edfcc0a64675b7f7ede04be00f
    fd2b210383358fe7697f201e19ac9779879ba72a
    afc397376ec50e96b2918ee64e48baf4dda0d37d

5. The testcase from MySQL relies heavily on sleep and timing for
testing, and seems likely to sporadically fail on heavily loaded test
servers in buildbot or distro build farms.

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/sql/log.cc b/sql/log.cc
index be24bcd718a..e3d42a4547e 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -4292,6 +4292,10 @@ void MYSQL_BIN_LOG::wait_for_last_checkpoint_event()
   relay log.
 
   IMPLEMENTATION
+
+  - You must hold rli->data_lock before calling this function, since
+    it writes group_relay_log_pos and similar fields of
+    Relay_log_info.
   - Protects index file with LOCK_index
   - Delete relevant relay log files
   - Copy all file names after these ones to the front of the index file
@@ -4305,7 +4309,7 @@ void MYSQL_BIN_LOG::wait_for_last_checkpoint_event()
                       read by the SQL slave thread are deleted).
 
   @note
-    - This is only called from the slave-execute thread when it has read
+    - This is only called from the slave SQL thread when it has read
     all commands from a relay log and want to switch to a new relay log.
     - When this happens, we can be in an active transaction as
     a transaction can span over two relay logs
@@ -4336,6 +4340,8 @@ int MYSQL_BIN_LOG::purge_first_log(Relay_log_info* rli, bool included)
   DBUG_ASSERT(rli->slave_running == MYSQL_SLAVE_RUN_NOT_CONNECT);
   DBUG_ASSERT(!strcmp(rli->linfo.log_file_name,rli->event_relay_log_name));
 
+  mysql_mutex_assert_owner(&rli->data_lock);
+
   mysql_mutex_lock(&LOCK_index);
 
   ir= rli->inuse_relaylog_list;