From ac2db256d9a390269a891a2addccf8ae1453cdb2 Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.org>
Date: Tue, 3 Oct 2017 21:07:27 +0200
Subject: [PATCH] MDEV-12874 UPDATE statements with the same source and target

fix --ps-protocol
---
 sql/sql_prepare.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 4df92c71006..9de0a6d0e99 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -1400,6 +1400,7 @@ static int mysql_test_update(Prepared_statement *stmt,
   int res;
   THD *thd= stmt->thd;
   uint table_count= 0;
+  TABLE_LIST *update_source_table;
   SELECT_LEX *select= &stmt->lex->select_lex;
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   uint          want_privilege;
@@ -1413,9 +1414,11 @@ static int mysql_test_update(Prepared_statement *stmt,
   if (mysql_handle_derived(thd->lex, DT_INIT))
     goto error;
 
-  if (table_list->is_multitable())
+  if (((update_source_table= unique_table(thd, table_list,
+                                          table_list->next_global, 0)) ||
+        table_list->is_multitable()))
   {
-    DBUG_ASSERT(table_list->view != 0);
+    DBUG_ASSERT(update_source_table || table_list->view != 0);
     DBUG_PRINT("info", ("Switch to multi-update"));
     /* pass counter value */
     thd->lex->table_count= table_count;