MDEV-23033: All slaves crash once in ~24 hours and loop restart with signal 11

Problem:
=======
Upon deleting or updating a row in a parent table (with primary key), if
the child table has virtual column and an associated key with ON UPDATE
CASCADE/ON DELETE CASCADE, it will result in slave crash.

Analysis:
========
Tables which are related through foreign key require prelocking similar to
triggers. i.e If a table has triggers/foreign keys we should add all tables
and routines used by them to the prelocking set.  This prelocking happens
during 'open_and_lock_tables' call.  Each table being opened is checked for
foreign key references. If foreign key reference exists then the child
table is opened and it is linked to the table_list. Upon any modification
to  parent table its corresponding child tables are retried from table_list
and they are updated accordingly. This prelocking work fine on master.

On slave  prelocking works for following cases.
 - Statement/mixed based replication
 - In row based replication when trigger execution is enabled through
   'slave_run_triggers_for_rbr=YES/LOGGING/ENFORCE'

Otherwise it results in an assert/crash, as the parent table will not find
the corresponding child table and it will be NULL. Dereferencing NULL
pointer leads to slave server exit.

Fix:
===
Introduce a new 'slave_fk_event_map' flag similar to 'trg_event_map'. This
flag will ensure that when foreign key is enabled in row based replication
all the parent and child tables are prelocked, so that parent is able to
locate the child table.

Note: This issue is specific to slave, hence only slave needs to be
      upgraded.

1 files changed, 5 insertions, 1 deletions

diff --git a/sql/table.h b/sql/table.h
index 9a864f7ce9f..57706655d9b 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -2277,8 +2277,12 @@ struct TABLE_LIST
     Indicates what triggers we need to pre-load for this TABLE_LIST
     when opening an associated TABLE. This is filled after
     the parsed tree is created.
+
+    slave_fk_event_map is filled on the slave side with bitmaps value
+    representing row-based event operation to help find and prelock
+    possible FK constrain-related child tables.
   */
-  uint8 trg_event_map;
+  uint8 trg_event_map, slave_fk_event_map;
   /* TRUE <=> this table is a const one and was optimized away. */
   bool optimized_away;