MDEV-14404 Don't use LEX::check_exists in ALTER SEQUENCE

sql/sql_alter.h

@@ -387,13 +387,15 @@ class Sql_cmd_alter_table : public Sql_cmd_common_alter_table
 /**
   Sql_cmd_alter_sequence represents the ALTER SEQUENCE statement.
 */
-class Sql_cmd_alter_sequence : public Sql_cmd
+class Sql_cmd_alter_sequence : public Sql_cmd,
+                               public DDL_options
 {
 public:
   /**
     Constructor, used to represent a ALTER TABLE statement.
   */
-  Sql_cmd_alter_sequence()
+  Sql_cmd_alter_sequence(const DDL_options &options)
+   :DDL_options(options)
   {}
 
   ~Sql_cmd_alter_sequence()

sql/sql_sequence.cc

@@ -851,10 +851,10 @@ bool Sql_cmd_alter_sequence::execute(THD *thd)
   if (check_grant(thd, ALTER_ACL, first_table, FALSE, UINT_MAX, FALSE))
     DBUG_RETURN(TRUE);                  /* purecov: inspected */
 
-  if (lex->check_exists)
+  if (if_exists())
     thd->push_internal_handler(&no_such_table_handler);
   error= open_and_lock_tables(thd, first_table, FALSE, 0);
-  if (lex->check_exists)
+  if (if_exists())
   {
     trapped_errors= no_such_table_handler.safely_trapped_errors();
     thd->pop_internal_handler();

sql/sql_yacc.yy

@@ -7314,7 +7314,7 @@ alter:
             Lex->create_info.set($2);
             Lex->sql_command= SQLCOM_ALTER_USER;
           }
-        | ALTER SEQUENCE_SYM opt_if_exists_table_element
+        | ALTER SEQUENCE_SYM opt_if_exists
           {
             LEX *lex= Lex;
             lex->name= null_clex_str;
@@ -7337,7 +7337,7 @@ alter:
           sequence_defs
           {
             /* Create a generic ALTER SEQUENCE statment. */
-            Lex->m_sql_cmd= new (thd->mem_root) Sql_cmd_alter_sequence();
+            Lex->m_sql_cmd= new (thd->mem_root) Sql_cmd_alter_sequence($3);
             if (Lex->m_sql_cmd == NULL)
               MYSQL_YYABORT;
           }

sql/sql_yacc_ora.yy

@@ -7301,7 +7301,7 @@ alter:
             Lex->create_info.set($2);
             Lex->sql_command= SQLCOM_ALTER_USER;
           }
-        | ALTER SEQUENCE_SYM opt_if_exists_table_element
+        | ALTER SEQUENCE_SYM opt_if_exists
           {
             LEX *lex= Lex;
             lex->name= null_clex_str;
@@ -7324,7 +7324,7 @@ alter:
           sequence_defs
           {
             /* Create a generic ALTER SEQUENCE statment. */
-            Lex->m_sql_cmd= new (thd->mem_root) Sql_cmd_alter_sequence();
+            Lex->m_sql_cmd= new (thd->mem_root) Sql_cmd_alter_sequence($3);
             if (Lex->m_sql_cmd == NULL)
               MYSQL_YYABORT;
           }