Fixed bug mdev-11818.

When a query containing a WITH clause is printed by EXPLAIN
EXTENDED command there should not be any data expansion in
the query specifications of the WITH elements of this WITH
clause.

mysql-test/r/cte_nonrecursive.result

@@ -927,3 +927,15 @@ Sergei Golubchik	Development	DE
 Claudio Nanni	Support	ES
 Sergei Petrunia	Development	RU
 drop table employees;
+#
+# MDEV-11818: EXPLAIN EXTENDED for a query with optimized away CTE table
+#
+CREATE TABLE t1 (i INT, c VARCHAR(3));
+INSERT INTO t1 VALUES (1,'foo');
+EXPLAIN EXTENDED
+WITH cte AS ( SELECT * FROM t1 ) SELECT i FROM cte;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	100.00	
+Warnings:
+Note	1003	with cte as (select `test`.`t1`.`i` AS `i`,`test`.`t1`.`c` AS `c` from `test`.`t1`)select 1 AS `i` from dual
+DROP TABLE t1;

mysql-test/t/cte_nonrecursive.test

@@ -609,3 +609,15 @@ where
               and T2.name <> T1.name);
 
 drop table employees;
+
+--echo #
+--echo # MDEV-11818: EXPLAIN EXTENDED for a query with optimized away CTE table
+--echo #
+
+CREATE TABLE t1 (i INT, c VARCHAR(3));
+INSERT INTO t1 VALUES (1,'foo');
+
+EXPLAIN EXTENDED
+WITH cte AS ( SELECT * FROM t1 ) SELECT i FROM cte;
+
+DROP TABLE t1;

sql/sql_cte.cc

@@ -1246,6 +1246,12 @@ bool st_select_lex::check_subqueries_with_recursive_references()
 
 void With_clause::print(String *str, enum_query_type query_type)
 {
+  /*
+    Any with clause contains just definitions of CTE tables.
+    No data expansion is applied to these definitions.
+  */
+  query_type= (enum_query_type) (query_type | QT_NO_DATA_EXPANSION);
+
   str->append(STRING_WITH_LEN("with "));
   if (with_recursive)
     str->append(STRING_WITH_LEN("recursive "));