MDEV-6139: UPDATE w/ join against MRG_MyISAM table with read-only sub-table failsUPDATE w/ join against MRG_MyISAM table with read-only sub-table fails

The problem was that on opening all tables TL_WRITE, than local tables which is not updated set to TL_READ, but underlying tables of MyISAMmrg left untouched.

Prartition engine has not this problem.

All cases where lock_type assigned is not changed because call of virtual function is not cheap.

2 files changed, 19 insertions, 0 deletions

diff --git a/storage/myisammrg/ha_myisammrg.cc b/storage/myisammrg/ha_myisammrg.cc
index 1ee974c1b23..388c9c9895d 100644
--- a/storage/myisammrg/ha_myisammrg.cc
+++ b/storage/myisammrg/ha_myisammrg.cc
@@ -1713,6 +1713,24 @@ my_bool ha_myisammrg::register_query_cache_dependant_tables(THD *thd
   DBUG_RETURN(FALSE);
 }
 
+
+void ha_myisammrg::ha_set_lock_type(enum thr_lock_type lock)
+{
+  handler::ha_set_lock_type(lock);
+  if (children_l != NULL)
+  {
+    for (TABLE_LIST *child_table= children_l;;
+         child_table= child_table->next_global)
+    {
+      child_table->lock_type=
+        child_table->table->reginfo.lock_type= lock;
+
+      if (&child_table->next_global == children_last_l)
+        break;
+    }
+  }
+}
+
 extern int myrg_panic(enum ha_panic_function flag);
 int myisammrg_panic(handlerton *hton, ha_panic_function flag)
 {
diff --git a/storage/myisammrg/ha_myisammrg.h b/storage/myisammrg/ha_myisammrg.h
index f5ba2ffef38..ce9c1917118 100644
--- a/storage/myisammrg/ha_myisammrg.h
+++ b/storage/myisammrg/ha_myisammrg.h
@@ -155,4 +155,5 @@ public:
                                           Query_cache *cache,
                                           Query_cache_block_table **block,
                                           uint *n);
+  virtual void ha_set_lock_type(enum thr_lock_type lock);
 };