Fixed mdev-14879 Lost rows for query using recursive CTE

with recursive reference in subquery

If a recursive CTE uses a subquery with recursive reference then
the virtual function reset() must be called after each iteration
performed at the execution of the CTE.

mysql-test/r/cte_recursive.result

@@ -2972,3 +2972,81 @@ WHERE 1 = 1
 ) K, t3;
 C	P	i
 drop table t1,t2,t3;
+#
+# mdev-14879: subquery with recursive reference in WHERE of CTE
+#
+create table flights
+(departure varchar(32),
+arrival varchar(32),
+carrier varchar(20),
+flight_number char(7));
+insert into flights values
+('Seattle', 'Frankfurt', 'Lufthansa', 'LH 491'),
+('Seattle', 'Chicago', 'American', 'AA 2573'),
+('Seattle', 'Los Angeles', 'Alaska Air', 'AS 410'),
+('Chicago', 'New York', 'American', 'AA 375'),
+('Chicago', 'Montreal', 'Air Canada', 'AC 3053'),
+('Los Angeles', 'New York', 'Delta', 'DL 1197'),
+('Moscow', 'Tokyo', 'Aeroflot', 'SU 264'),
+('New York', 'Paris', 'Air France', 'AF 23'),
+('Frankfurt', 'Moscow', 'Lufthansa', 'LH 1444'),
+('Tokyo', 'Seattle', 'ANA', 'NH 178'),
+('Los Angeles', 'Tokyo', 'ANA', 'NH 175'),
+('Moscow', 'Los Angeles', 'Aeroflot', 'SU 106'),
+('Montreal', 'Paris', 'Air Canada', 'AC 870'),
+('Cairo', 'Paris', 'Air France', 'AF 503'),
+('New York', 'Seattle', 'American', 'AA 45'),
+('Paris', 'Chicago', 'Air France', 'AF 6734');
+with recursive destinations (city) as
+( select a.arrival from flights a where a.departure='Cairo'
+  union
+select b.arrival from destinations r, flights b where r.city=b.departure)
+select * from destinations;
+city
+Paris
+Chicago
+New York
+Montreal
+Seattle
+Frankfurt
+Los Angeles
+Moscow
+Tokyo
+set standard_compliant_cte=0;
+with recursive destinations (city, legs) as
+(
+select a.arrival, 1 from flights a where a.departure='Cairo'
+  union
+select b.arrival, r.legs + 1 from destinations r, flights b
+where r.city=b.departure and b.arrival not in (select city from destinations)
+)
+select * from destinations;
+city	legs
+Paris	1
+Chicago	2
+New York	3
+Montreal	3
+Seattle	4
+Frankfurt	5
+Los Angeles	5
+Moscow	6
+Tokyo	6
+explain extended with recursive destinations (city, legs) as
+(
+select a.arrival, 1 from flights a where a.departure='Cairo'
+  union
+select b.arrival, r.legs + 1 from destinations r, flights b
+where r.city=b.departure and b.arrival not in (select city from destinations)
+)
+select * from destinations;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	16	100.00	
+2	DERIVED	a	ALL	NULL	NULL	NULL	NULL	16	100.00	Using where
+3	RECURSIVE UNION	b	ALL	NULL	NULL	NULL	NULL	16	100.00	Using where
+3	RECURSIVE UNION	<derived2>	ref	key0	key0	35	test.b.departure	2	100.00	
+4	DEPENDENT SUBQUERY	<derived2>	ALL	NULL	NULL	NULL	NULL	16	100.00	Using where
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
+Warnings:
+Note	1003	with recursive destinations as (select `test`.`a`.`arrival` AS `city`,1 AS `legs` from `test`.`flights` `a` where `test`.`a`.`departure` = 'Cairo' union select `test`.`b`.`arrival` AS `arrival`,`r`.`legs` + 1 AS `r.legs + 1` from `destinations` `r` join `test`.`flights` `b` where `r`.`city` = `test`.`b`.`departure` and !<in_optimizer>(`test`.`b`.`arrival`,<exists>(select `destinations`.`city` from `destinations` where trigcond(`test`.`b`.`arrival` = `destinations`.`city` or `destinations`.`city` is null) having trigcond(`destinations`.`city` is null))))select `destinations`.`city` AS `city`,`destinations`.`legs` AS `legs` from `destinations`
+set standard_compliant_cte=default;
+drop table flights;

mysql-test/t/cte_recursive.test

@@ -2032,3 +2032,56 @@ FROM
 ) K, t3;
 
 drop table t1,t2,t3;
+
+--echo #
+--echo # mdev-14879: subquery with recursive reference in WHERE of CTE
+--echo #
+
+create table flights
+(departure varchar(32),
+ arrival varchar(32),
+ carrier varchar(20),
+ flight_number char(7));
+
+insert into flights values
+('Seattle', 'Frankfurt', 'Lufthansa', 'LH 491'),
+('Seattle', 'Chicago', 'American', 'AA 2573'),
+('Seattle', 'Los Angeles', 'Alaska Air', 'AS 410'),
+('Chicago', 'New York', 'American', 'AA 375'),
+('Chicago', 'Montreal', 'Air Canada', 'AC 3053'),
+('Los Angeles', 'New York', 'Delta', 'DL 1197'),
+('Moscow', 'Tokyo', 'Aeroflot', 'SU 264'),
+('New York', 'Paris', 'Air France', 'AF 23'),
+('Frankfurt', 'Moscow', 'Lufthansa', 'LH 1444'),
+('Tokyo', 'Seattle', 'ANA', 'NH 178'),
+('Los Angeles', 'Tokyo', 'ANA', 'NH 175'),
+('Moscow', 'Los Angeles', 'Aeroflot', 'SU 106'),
+('Montreal', 'Paris', 'Air Canada', 'AC 870'),
+('Cairo', 'Paris', 'Air France', 'AF 503'),
+('New York', 'Seattle', 'American', 'AA 45'),
+('Paris', 'Chicago', 'Air France', 'AF 6734');
+
+with recursive destinations (city) as
+( select a.arrival from flights a where a.departure='Cairo'
+  union
+  select b.arrival from destinations r, flights b where r.city=b.departure)
+select * from destinations;
+
+set standard_compliant_cte=0;
+
+let $q=
+with recursive destinations (city, legs) as
+(
+  select a.arrival, 1 from flights a where a.departure='Cairo'
+  union
+  select b.arrival, r.legs + 1 from destinations r, flights b
+  where r.city=b.departure and b.arrival not in (select city from destinations)
+)
+select * from destinations;
+
+eval $q;
+eval explain extended $q;
+
+set standard_compliant_cte=default;
+
+drop table flights;

sql/sql_union.cc

@@ -1284,6 +1284,7 @@ bool st_select_lex_unit::exec_recursive()
        sq;
        sq= sq->next_with_rec_ref)
   {
+    sq->reset();
     sq->engine->force_reexecution();
   }