Correction of the merge 10.2 into 10.3 for MDEV-23619

(correction for commit 6fed6de9)

mysql-test/main/cte_recursive.result

@@ -1301,7 +1301,7 @@ select ancestors.name, ancestors.dob from ancestors;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<derived4>	ALL	NULL	NULL	NULL	NULL	24	
 4	DERIVED	folks	ALL	NULL	NULL	NULL	NULL	12	Using where
-6	RECURSIVE UNION	<derived3>	ALL	NULL	NULL	NULL	NULL	12	
+6	UNION	<derived3>	ALL	NULL	NULL	NULL	NULL	12	
 5	RECURSIVE UNION	<derived4>	ALL	NULL	NULL	NULL	NULL	24	
 NULL	UNION RESULT	<union4,6,5>	ALL	NULL	NULL	NULL	NULL	NULL	
 3	DERIVED	folks	ALL	NULL	NULL	NULL	NULL	12	Using where
@@ -4029,7 +4029,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 3	RECURSIVE UNION	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
 3	RECURSIVE UNION	<derived2>	ref	key0	key0	9	test.t1.c	2	
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
-4	RECURSIVE UNION	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
+4	UNION	<derived2>	ALL	NULL	NULL	NULL	NULL	4	
 with recursive r_cte as
 ( select * from t1 as s
 union

sql/sql_lex.cc

@@ -4712,16 +4712,16 @@ void st_select_lex::set_explain_type(bool on_the_fly)
               /*
                 pos_in_table_list=NULL for e.g. post-join aggregation JOIN_TABs.
               */
-              if (!tab->table);
-              else if (const TABLE_LIST *pos= tab->table->pos_in_table_list)
-              {
-                if (pos->with && pos->with->is_recursive)
+              if (!(tab->table && tab->table->pos_in_table_list))
+	        continue;
+              TABLE_LIST *tbl= tab->table->pos_in_table_list;
+              if (tbl->with && tbl->with->is_recursive &&
+                  tbl->is_with_table_recursive_reference())
               {
                 uses_cte= true;
                 break;
               }
             }
-            }
             if (uses_cte)
               type= "RECURSIVE UNION";
           }