MDEV-31361 Wrong result on 2nd execution of PS for query with derived table

This bug led to wrong result sets returned by the second execution of prepared statements from selects using mergeable derived tables pushed into external engine. Such derived tables are always materialized. The decision that they have to be materialized is taken late in the function mysql_derived_optimized(). For regular derived tables this decision is usually taken at the prepare phase. However in some cases for some derived tables this decision is made in mysql_derived_optimized() too. It can be seen in the code of mysql_derived_fill() that for such a derived table it's critical to change its translation table to tune it to the fields of the temporary table used for materialization of the derived table and this must be done after each refill of the derived table. The same actions are needed for derived tables pushed into external engines. Approved by Oleksandr Byelkin <sanja@mariadb.com>

Author: igorbabaev

mysql-test/suite/federated/federatedx_create_handlers.result

@@ -496,6 +496,23 @@ use federated;
 SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
 WHERE id=2) dt2) dt;
 id	name
+PREPARE stmt FROM "
+SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
+ WHERE id=3) dt2) dt;
+";
+EXECUTE stmt;
+id	name
+3	xxx
+EXECUTE stmt;
+id	name
+3	xxx
+DEALLOCATE PREPARE stmt;
+EXPLAIN
+SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
+WHERE id=3) dt2) dt;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived4>	ALL	NULL	NULL	NULL	NULL	5	Using where
+4	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 connection slave;
 CREATE TABLE federated.t10 (a INT,b INT);
 CREATE TABLE federated.t11 (a INT, b INT);
@@ -516,6 +533,54 @@ WHERE id=2) dt2) dt
 a	b	a	b	id	name
 1	1	NULL	NULL	NULL	NULL
 2	2	NULL	NULL	NULL	NULL
+#
+# MDEV-31361: Second execution of PS for query with derived table
+#
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+CREATE TABLE federated.t1 (
+id int(20) NOT NULL,
+name varchar(16) NOT NULL default ''
+)
+DEFAULT CHARSET=latin1;
+INSERT INTO federated.t1 VALUES
+(3,'xxx'), (7,'yyy'), (4,'xxx'), (1,'zzz'), (5,'yyy');
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+CREATE TABLE federated.t1 (
+id int(20) NOT NULL,
+name varchar(16) NOT NULL default ''
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:SLAVE_PORT/federated/t1';
+use federated;
+SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM t1 where id>3) dt3
+WHERE id>3) dt2
+) dt;
+id	name
+7	yyy
+4	xxx
+5	yyy
+PREPARE stmt FROM "SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM
+(SELECT * FROM t1 where id>3) dt3
+WHERE id>3) dt2
+) dt";
+EXECUTE stmt;
+id	name
+7	yyy
+4	xxx
+5	yyy
+EXECUTE stmt;
+id	name
+7	yyy
+4	xxx
+5	yyy
+DEALLOCATE PREPARE stmt;
 set global federated_pushdown=0;
 connection master;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/suite/federated/federatedx_create_handlers.test

@@ -94,12 +94,9 @@ DEFAULT CHARSET=latin1;
 INSERT INTO federated.t3 VALUES
  ('yyy'), ('www'), ('yyy'), ('xxx'), ('www'), ('yyy'), ('www');
 
-#Enable after fix MDEV-31361
---disable_ps2_protocol
 SELECT *
 FROM federated.t3, (SELECT * FROM federated.t1 WHERE id > 3) t
 WHERE federated.t3.name=t.name;
---enable_ps2_protocol
 
 EXPLAIN
 SELECT *
@@ -351,6 +348,18 @@ use federated;
 SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
  WHERE id=2) dt2) dt;
 
+PREPARE stmt FROM "
+SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
+ WHERE id=3) dt2) dt;
+";
+EXECUTE stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
+EXPLAIN
+SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT * FROM t1 where id=3) dt3
+ WHERE id=3) dt2) dt;
+
 connection slave;
 CREATE TABLE federated.t10 (a INT,b INT);
 CREATE TABLE federated.t11 (a INT, b INT);
@@ -376,6 +385,52 @@ SELECT * FROM t10 LEFT JOIN
  WHERE id=2) dt2) dt
  ) ON t10.a=t11.a;
 
+--echo #
+--echo # MDEV-31361: Second execution of PS for query with derived table
+--echo #
+
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+
+CREATE TABLE federated.t1 (
+ id int(20) NOT NULL,
+ name varchar(16) NOT NULL default ''
+)
+DEFAULT CHARSET=latin1;
+
+INSERT INTO federated.t1 VALUES
+ (3,'xxx'), (7,'yyy'), (4,'xxx'), (1,'zzz'), (5,'yyy');
+
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+eval
+CREATE TABLE federated.t1 (
+ id int(20) NOT NULL,
+ name varchar(16) NOT NULL default ''
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:$SLAVE_MYPORT/federated/t1';
+
+use federated;
+
+let $q=
+SELECT * FROM
+ (SELECT * FROM
+ (SELECT * FROM
+ (SELECT * FROM t1 where id>3) dt3
+ WHERE id>3) dt2
+ ) dt;
+
+eval $q;
+
+eval PREPARE stmt FROM "$q";
+EXECUTE stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
+
 set global federated_pushdown=0;
 
 source include/federated_cleanup.inc;

sql/sql_derived.cc

@@ -1217,7 +1217,9 @@ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
  /* Execute the query that specifies the derived table by a foreign engine */
  res= derived->pushdown_derived->execute();
  unit->executed= true;
+ if (res)
  DBUG_RETURN(res);
+ goto after_exec;
  }
 
  if (unit->executed && !derived_is_recursive &&
@@ -1278,6 +1280,7 @@ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
  derived_result, unit, first_select);
  }
 
+ after_exec:
  if (!res && !derived_is_recursive)
  {
  if (derived_result->flush())