From c4930a820aeba156169b157971223bed81ea1876 Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.org>
Date: Mon, 5 Feb 2018 16:00:13 +0100
Subject: [PATCH] don't set derived->merged until derived is really
 irreversibly merged

it was set before big if() that could decide not to merge and
go with materialization.

this fixes a crash in main.view test
---
 sql/sql_derived.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc
index 60827bd1772..0147271f068 100644
--- a/sql/sql_derived.cc
+++ b/sql/sql_derived.cc
@@ -388,7 +388,6 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
    thd->save_prep_leaf_list= TRUE;
 
   arena= thd->activate_stmt_arena_if_needed(&backup);  // For easier test
-  derived->merged= TRUE;
 
   if (!derived->merged_for_insert || 
       (derived->is_multitable() && 
@@ -452,6 +451,7 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived)
     if (parent_lex->join) 
       parent_lex->join->table_count+= dt_select->join->table_count - 1;
   }
+  derived->merged= TRUE;
   if (derived->get_unit()->prepared)
   {
     Item *expr= derived->on_expr;