Fix LP bug lp:802979

Analysis:
This bug consists of two related problems that are
result of too early evaluation of single-row subqueries
during the optimization phase of the outer query.

Several optimizer code paths try to evaluate single-row
subqueries in order to produce a constant and use that
constant for further optimzation.

When the execution of the subquery peforms destructive
changes to the representation of the subquery, and these
changes are not anticipated by the subsequent optimization
phases of the outer query, we tipically get a crash or
failed assert.

Specifically, in this bug the inner-most suqbuery with
DISTINCT triggers a substitution of the original JOIN
object by a single-table JOIN object with a temp table
needed to perform the DISTINCT operation (created by
JOIN::make_simple_join).

This substitution breaks EXPLAIN because:
a) in the first example JOIN::cleanup no longer can
reach the original table of the innermost subquery, and
close all indexes, and
b) in this second test query, EXPLAIN attempts to print
the name of the internal temp table, and crashes because
the temp table has no name (NULL pointer instead).

Solution:
a) fully disable subquery evaluation during optimization
in all cases - both for constant propagation and range
optimization, and
b) change JOIN::join_free() to perform cleanup irrespective
of EXPLAIN or not.

mysql-test/r/group_min_max.result

@@ -2412,7 +2412,7 @@ EXPLAIN SELECT 1 FROM t1 AS t1_outer1 JOIN t1 AS t1_outer2
 ON t1_outer1.a = (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) 
 AND t1_outer1.b = t1_outer2.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1_outer1	ref	a	a	5	const	1	Using index
+1	PRIMARY	t1_outer1	ref	a	a	5	const	2	Using where; Using index
 1	PRIMARY	t1_outer2	index	NULL	a	10	NULL	15	Using where; Using index; Using join buffer (flat, BNL join)
 2	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by
 EXPLAIN SELECT (SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x
@@ -2749,7 +2749,7 @@ NULL
 EXPLAIN
 SELECT MIN( a ) FROM t1 WHERE a = (SELECT a FROM t1 WHERE a < 0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-x	x	x	x	x	x	x	x	x	Impossible WHERE noticed after reading const tables
+x	x	x	x	x	x	x	x	x	Using where; Using index
 x	x	x	x	x	x	x	x	x	Using where; Using index
 SELECT MIN( a ) FROM t1 WHERE a = (SELECT a FROM t1 WHERE a < 0);
 MIN( a )
@@ -2821,7 +2821,7 @@ NULL
 EXPLAIN
 SELECT MIN( a ) FROM t1 WHERE a = (SELECT a FROM t1 WHERE a < 0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-x	x	x	x	x	x	x	x	x	Impossible WHERE noticed after reading const tables
+x	x	x	x	x	x	x	x	x	Using where; Using index
 x	x	x	x	x	x	x	x	x	Using where; Using index
 SELECT MIN( a ) FROM t1 WHERE a = (SELECT a FROM t1 WHERE a < 0);
 MIN( a )

mysql-test/r/sp.result

@@ -6420,16 +6420,16 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	c1	c1	5	const	1	Using index
 EXPLAIN SELECT * FROM t1 WHERE c1=f1();
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	c1	c1	5	const	1	Using index
+1	SIMPLE	t1	ref	c1	c1	5	const	0	Using index
 EXPLAIN SELECT * FROM v1 WHERE c1=1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	c1	c1	5	const	1	Using index
 EXPLAIN SELECT * FROM v1 WHERE c1=f1();
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	c1	c1	5	const	1	Using index
+1	SIMPLE	t1	ref	c1	c1	5	const	0	Using index
 EXPLAIN SELECT * FROM t1 WHERE c1=f2(10);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	c1	c1	5	const	1	Using index
+1	SIMPLE	t1	ref	c1	c1	5	const	0	Using index
 EXPLAIN SELECT * FROM t1 WHERE c1=f2(c1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	NULL	c1	5	NULL	5	Using where; Using index

mysql-test/r/subselect.result

@@ -551,7 +551,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	100.00	Using index
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = 3))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where multiple equal(1, `test`.`t1`.`numeropost`))))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1236,7 +1236,7 @@ create table t1 (id int not null auto_increment primary key, salary int, key(sal
 insert into t1 (salary) values (100),(1000),(10000),(10),(500),(5000),(50000);
 explain extended SELECT id FROM t1 where salary = (SELECT MAX(salary) FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using index condition
+1	PRIMARY	t1	ref	salary	salary	5	const	0	0.00	Using index condition
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
 Note	1003	select `test`.`t1`.`id` AS `id` from `test`.`t1` where (`test`.`t1`.`salary` = (select max(`test`.`t1`.`salary`) from `test`.`t1`))
@@ -4030,7 +4030,7 @@ CREATE TABLE t1 (a int, b int, KEY (a));
 INSERT INTO t1 VALUES (1,1),(2,1);
 EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT COUNT(*) FROM t1 GROUP BY b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ref	a	a	5	const	1	Using where; Using index
+1	PRIMARY	t1	ref	a	a	5	const	0	Using where; Using index
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
 DROP TABLE t1;
 CREATE TABLE t1 (id int NOT NULL, st CHAR(2), INDEX idx(id));

mysql-test/r/subselect4.result

@@ -731,7 +731,7 @@ WHERE f3 = (
 SELECT t1.f3 FROM t1
 WHERE ( t1.f10 ) IN ( SELECT f11 FROM t2 GROUP BY f11 ));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	t1	ref	f3	f3	5	const	0	Using index condition
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
 2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	5	test.t1.f10	1	
 3	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using temporary
@@ -746,7 +746,7 @@ WHERE f3 = (
 SELECT f3 FROM t1
 WHERE ( f10, f10 ) IN ( SELECT f11, f11 FROM t2 GROUP BY f11 ));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	t1	ref	f3	f3	5	const	0	Using index condition
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
 2	SUBQUERY	<subquery3>	eq_ref	distinct_key	distinct_key	10	test.t1.f10,test.t1.f10	1	
 3	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using temporary
@@ -1736,3 +1736,49 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	2	
 3	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary
 drop table t1, t2, t3;
+#
+# LP BUG#802979 Assertion `table->key_read == 0' in close_thread_table
+#
+CREATE TABLE t1 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t1 VALUES (1,0),(5,0);
+CREATE TABLE t2 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t2 VALUES (1,0),(5,0);
+CREATE TABLE t3 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t3 VALUES (1,0),(5,0);
+CREATE TABLE t4 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t4 VALUES (1,0),(5,0);
+EXPLAIN
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+WHERE EXISTS (SELECT DISTINCT f1 FROM t4))
+AND t2.f2 = t1.f1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	f1	f1	5	const	0	Using index condition
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
+2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	2	
+3	SUBQUERY	t4	index	NULL	f1	5	NULL	2	Using index; Using temporary
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+WHERE EXISTS (SELECT DISTINCT f1 FROM t4))
+AND t2.f2 = t1.f1;
+ERROR 21000: Subquery returns more than 1 row
+EXPLAIN
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+WHERE EXISTS (SELECT DISTINCT f1 FROM t4) LIMIT 1)
+AND t2.f2 = t1.f1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	f1	f1	5	const	0	Using index condition
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
+2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	2	
+3	SUBQUERY	t4	index	NULL	f1	5	NULL	2	Using index; Using temporary
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+WHERE EXISTS (SELECT DISTINCT f1 FROM t4) LIMIT 1)
+AND t2.f2 = t1.f1;
+f1	f2	f1	f2
+drop table t1,t2,t3,t4;

mysql-test/r/subselect_no_mat.result

@@ -555,7 +555,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	100.00	Using index
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = 3))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where multiple equal(1, `test`.`t1`.`numeropost`))))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1240,7 +1240,7 @@ create table t1 (id int not null auto_increment primary key, salary int, key(sal
 insert into t1 (salary) values (100),(1000),(10000),(10),(500),(5000),(50000);
 explain extended SELECT id FROM t1 where salary = (SELECT MAX(salary) FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using index condition
+1	PRIMARY	t1	ref	salary	salary	5	const	0	0.00	Using index condition
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
 Note	1003	select `test`.`t1`.`id` AS `id` from `test`.`t1` where (`test`.`t1`.`salary` = (select max(`test`.`t1`.`salary`) from `test`.`t1`))
@@ -4034,7 +4034,7 @@ CREATE TABLE t1 (a int, b int, KEY (a));
 INSERT INTO t1 VALUES (1,1),(2,1);
 EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT COUNT(*) FROM t1 GROUP BY b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ref	a	a	5	const	1	Using where; Using index
+1	PRIMARY	t1	ref	a	a	5	const	0	Using where; Using index
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
 DROP TABLE t1;
 CREATE TABLE t1 (id int NOT NULL, st CHAR(2), INDEX idx(id));

mysql-test/r/subselect_no_opts.result

@@ -552,7 +552,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	100.00	Using index
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = 3))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where multiple equal(1, `test`.`t1`.`numeropost`))))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1237,7 +1237,7 @@ create table t1 (id int not null auto_increment primary key, salary int, key(sal
 insert into t1 (salary) values (100),(1000),(10000),(10),(500),(5000),(50000);
 explain extended SELECT id FROM t1 where salary = (SELECT MAX(salary) FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using index condition
+1	PRIMARY	t1	ref	salary	salary	5	const	0	0.00	Using index condition
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
 Note	1003	select `test`.`t1`.`id` AS `id` from `test`.`t1` where (`test`.`t1`.`salary` = (select max(`test`.`t1`.`salary`) from `test`.`t1`))
@@ -4031,7 +4031,7 @@ CREATE TABLE t1 (a int, b int, KEY (a));
 INSERT INTO t1 VALUES (1,1),(2,1);
 EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT COUNT(*) FROM t1 GROUP BY b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ref	a	a	5	const	1	Using where; Using index
+1	PRIMARY	t1	ref	a	a	5	const	0	Using where; Using index
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
 DROP TABLE t1;
 CREATE TABLE t1 (id int NOT NULL, st CHAR(2), INDEX idx(id));

mysql-test/r/subselect_no_semijoin.result

@@ -552,7 +552,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	100.00	Using index
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
-Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = 3))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((3 = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where multiple equal(1, `test`.`t1`.`numeropost`))))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1237,7 +1237,7 @@ create table t1 (id int not null auto_increment primary key, salary int, key(sal
 insert into t1 (salary) values (100),(1000),(10000),(10),(500),(5000),(50000);
 explain extended SELECT id FROM t1 where salary = (SELECT MAX(salary) FROM t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using index condition
+1	PRIMARY	t1	ref	salary	salary	5	const	0	0.00	Using index condition
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 Warnings:
 Note	1003	select `test`.`t1`.`id` AS `id` from `test`.`t1` where (`test`.`t1`.`salary` = (select max(`test`.`t1`.`salary`) from `test`.`t1`))
@@ -4031,7 +4031,7 @@ CREATE TABLE t1 (a int, b int, KEY (a));
 INSERT INTO t1 VALUES (1,1),(2,1);
 EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT COUNT(*) FROM t1 GROUP BY b);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ref	a	a	5	const	1	Using where; Using index
+1	PRIMARY	t1	ref	a	a	5	const	0	Using where; Using index
 2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
 DROP TABLE t1;
 CREATE TABLE t1 (id int NOT NULL, st CHAR(2), INDEX idx(id));

mysql-test/t/subselect4.test

@@ -1415,3 +1415,45 @@ WHERE t2.f1 = (
                 FROM t1));
 
 drop table t1, t2, t3;
+
+--echo #
+--echo # LP BUG#802979 Assertion `table->key_read == 0' in close_thread_table
+--echo #
+
+CREATE TABLE t1 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t1 VALUES (1,0),(5,0);
+CREATE TABLE t2 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t2 VALUES (1,0),(5,0);
+CREATE TABLE t3 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t3 VALUES (1,0),(5,0);
+CREATE TABLE t4 ( f1 int, f2 int , KEY (f1)) ;
+INSERT IGNORE INTO t4 VALUES (1,0),(5,0);
+
+EXPLAIN
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+               WHERE EXISTS (SELECT DISTINCT f1 FROM t4))
+  AND t2.f2 = t1.f1;
+
+-- error ER_SUBQUERY_NO_1_ROW
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+               WHERE EXISTS (SELECT DISTINCT f1 FROM t4))
+  AND t2.f2 = t1.f1;
+
+EXPLAIN
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+               WHERE EXISTS (SELECT DISTINCT f1 FROM t4) LIMIT 1)
+  AND t2.f2 = t1.f1;
+
+SELECT *
+FROM t1, t2
+WHERE t2.f2 = (SELECT f2 FROM t3
+               WHERE EXISTS (SELECT DISTINCT f1 FROM t4) LIMIT 1)
+  AND t2.f2 = t1.f1;
+
+drop table t1,t2,t3,t4;

sql/opt_range.cc

@@ -7292,7 +7292,7 @@ static SEL_TREE *get_mm_tree(RANGE_OPT_PARAM *param,COND *cond)
   case Item_func::MULT_EQUAL_FUNC:
   {
     Item_equal *item_equal= (Item_equal *) cond;    
-    if (!(value= item_equal->get_const()))
+    if (!(value= item_equal->get_const()) || value->is_expensive())
       DBUG_RETURN(0);
     Item_equal_fields_iterator it(*item_equal);
     ref_tables= value->used_tables();
@@ -7325,6 +7325,9 @@ static SEL_TREE *get_mm_tree(RANGE_OPT_PARAM *param,COND *cond)
     }
     else
       DBUG_RETURN(0);
+    if (value && value->is_expensive())
+      DBUG_RETURN(0);
+
     ftree= get_full_func_mm_tree(param, cond_func, field_item, value, inv);
   }
 

sql/sql_select.cc

@@ -9620,8 +9620,7 @@ void JOIN::join_free()
     Optimization: if not EXPLAIN and we are done with the JOIN,
     free all tables.
   */
-  bool full= (!(select_lex->uncacheable) &&
-              !thd->lex->describe);
+  bool full= !(select_lex->uncacheable);
   bool can_unlock= full;
   DBUG_ENTER("JOIN::join_free");
 
@@ -11472,8 +11471,8 @@ propagate_cond_constants(THD *thd, I_List<COND_CMP> *save_list,
     {
       Item_func_eq *func=(Item_func_eq*) cond;
       Item **args= func->arguments();
-      bool left_const= args[0]->const_item();
-      bool right_const= args[1]->const_item();
+      bool left_const= args[0]->const_item() && !args[0]->is_expensive();
+      bool right_const= args[1]->const_item() && !args[1]->is_expensive();
       if (!(left_const && right_const) &&
           args[0]->result_type() == args[1]->result_type())
       {