MDEV-10235: Deadlock in CREATE TABLE .. AS SELECT .. if result set is empty in Galera

In CTAS, handlers get registered under statement transaction
(st_transactions::stmt), while ha_fake_trx_id(), used by CTAS,
looked under standard transaction (st_transactions::all) for
registered handlers, and thus it failed to grab a fake transaction
ID. As a result, with no valid transaction ID, wsrep commit failed
with an error.

ha_fake_trx_id() now looks for handlers registered under 'stmt'
in case 'all' is empty. Also modified the logic to print warning
only once if none of the registered handlers have fake_trx_id.

1 files changed, 22 insertions, 5 deletions

diff --git a/sql/handler.cc b/sql/handler.cc
index 49e451e3836..147221abb97 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -6104,25 +6104,42 @@ int ha_abort_transaction(THD *bf_thd, THD *victim_thd, my_bool signal)
 void ha_fake_trx_id(THD *thd)
 {
   DBUG_ENTER("ha_fake_trx_id");
+
+  bool no_fake_trx_id= true;
+
   if (!WSREP(thd))
   {
     DBUG_VOID_RETURN;
   }
 
-  THD_TRANS *trans= &thd->transaction.all;
+  /* Try statement transaction if standard one is not set. */
+  THD_TRANS *trans= (thd->transaction.all.ha_list) ?  &thd->transaction.all :
+    &thd->transaction.stmt;
+
   Ha_trx_info *ha_info= trans->ha_list, *ha_info_next;
 
   for (; ha_info; ha_info= ha_info_next)
   {
     handlerton *hton= ha_info->ht();
-    if (!hton->fake_trx_id)
+    if (hton->fake_trx_id)
     {
-      WSREP_WARN("cannot get fake InnoDB transaction ID");
-    }
-    else
       hton->fake_trx_id(hton, thd);
+
+      /* Got a fake trx id. */
+      no_fake_trx_id= false;
+
+      /*
+        We need transaction ID from just one storage engine providing
+        fake_trx_id (which will most likely be the case).
+      */
+      break;
+    }
     ha_info_next= ha_info->next();
   }
+
+  if (unlikely(no_fake_trx_id))
+    WSREP_WARN("Cannot get fake transaction ID from storage engine.");
+
   DBUG_VOID_RETURN;
 }
 #endif /* WITH_WSREP */