From b15a5f6fff8f66a3d51e483785461ab442df0e3f Mon Sep 17 00:00:00 2001
From: Aleksey Midenkov <midenok@gmail.com>
Date: Mon, 11 Oct 2021 15:28:00 +0300
Subject: [PATCH] MDEV-26767 Server crashes when rename table and alter storage
 engine

Wrong assertion leftover removed. m_sql_cmd can be allocated by any
ALTER subcommand and before allocation it is checked for NULL first.
---
 mysql-test/main/alter_table.result | 5 +++++
 mysql-test/main/alter_table.test   | 6 ++++++
 sql/sql_lex.cc                     | 1 -
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/alter_table.result b/mysql-test/main/alter_table.result
index a2830b95294..bef7f393d1d 100644
--- a/mysql-test/main/alter_table.result
+++ b/mysql-test/main/alter_table.result
@@ -3375,3 +3375,8 @@ drop table t1;
 #
 # End of 10.5 tests
 #
+#
+# MDEV-26767 Server crashes when rename table and alter storage engine
+#
+alter table txxx engine=innodb, rename to tyyy;
+ERROR 42S02: Table 'test.txxx' doesn't exist
diff --git a/mysql-test/main/alter_table.test b/mysql-test/main/alter_table.test
index d81f50e096c..4bf5eed5a43 100644
--- a/mysql-test/main/alter_table.test
+++ b/mysql-test/main/alter_table.test
@@ -2570,3 +2570,9 @@ drop table t1;
 --echo #
 --echo # End of 10.5 tests
 --echo #
+
+--echo #
+--echo # MDEV-26767 Server crashes when rename table and alter storage engine
+--echo #
+--error ER_NO_SUCH_TABLE
+alter table txxx engine=innodb, rename to tyyy;
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 503f750fe61..f2fa44ad9c2 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -11260,7 +11260,6 @@ bool LEX::stmt_alter_table_exchange_partition(Table_ident *table)
 bool LEX::stmt_alter_table(Table_ident *table)
 {
   DBUG_ASSERT(sql_command == SQLCOM_ALTER_TABLE);
-  DBUG_ASSERT(!m_sql_cmd);
   first_select_lex()->db= table->db;
   if (first_select_lex()->db.str == NULL &&
       copy_db_to(&first_select_lex()->db))