MDEV-19158: MariaDB 10.2.22 is writing duplicate entries into binary log

Problem:
========
We have a Master/Master Setup on two servers, but are only writing to one of
those servers (so it is essentially Master/Slave) We upgraded from 10.1.* to
10.2.22 last week and starting with the upgrade, we are getting duplicate key
errors on the slave. BINLOG=mixed.

Analysis:
=========
This issue happens with LOCK TABLES and binlog_format=MIXED combination. When an
UNSAFE statement is encountered in 'MIXED' mode, it is logged in the form of
'ROW' format. For all the tables that are part of LOCK TABLES list their table maps
are written into the binary log. For each table in the list a check is
done to see if 'check_table_binlog_row_based_done' flag is set or not. If it is not set
a check process is initiated to see if table qualifies for row based binary
logging or not and 'check_table_binlog_row_based_done' is set. This flag will be
cleared at the time of closing thread tables.

But there can be special cases where the LOCK TABLES contains more number of
tables but the unsafe query is actually using subset of tables from LOCK TABLES
list.

For example: LOCK TABLES locks t1,t2,t3 but the unsafe statement makes use of
only two tables t1,t3. In this case the 'check_table_binlog_row_based_done' flag
is enabled for table 't2' while writing table map, but 'close_thread_tables'
function call will not reset this flag. Since the flag is not cleared for table
't2' even a safe statement which used t2 will be logged in the form of row based
format.

This leads to an assert on debug builds and causes duplicate entries in release
builds. In release builds a statement is logged in the form of both ROW and
STATEMENT format. This causes the slave to fail with duplicate key error.

Fix:
===
During 'close_thread_tables' when LOCK TABLE modes are active "ha_reset" is done
for all the tables which were part of current statement. As mentioned in the
example 'ha_reset' is called for tables 't1' and 't3'. This will clear the
'check_table_binlog_row_based_done' flag. At this point add a check for the rest
of the tables to see if 'check_table_binlog_row_based_done' is enabled or not.
If enabled clear the flag.

1 files changed, 8 insertions, 0 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index bda3e649ad3..035c29d8ebc 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -583,6 +583,12 @@ bool close_cached_connection_tables(THD *thd, LEX_STRING *connection)
     Marks all tables in the list which were used by current substatement
     (they are marked by its query_id) as free for reuse.
 
+    Clear 'check_table_binlog_row_based_done' flag. For tables which were used
+    by current substatement the flag is cleared as part of 'ha_reset()' call.
+    For the rest of the open tables not used by current substament if this
+    flag is enabled as part of current substatement execution, clear the flag
+    explicitly.
+
   NOTE
     The reason we reset query_id is that it's not enough to just test
     if table->query_id != thd->query_id to know if a table is in use.
@@ -604,6 +610,8 @@ static void mark_used_tables_as_free_for_reuse(THD *thd, TABLE *table)
       table->query_id= 0;
       table->file->ha_reset();
     }
+    else if (table->file->check_table_binlog_row_based_done)
+      table->file->clear_cached_table_binlog_row_based_flag();
   }
 }