Fix for MDEV-4144

  
Analysis:
The reason for the inefficent plan was that Item_subselect::is_expensive()
didn't detect the special case when a subquery was optimized, but had no
join plan because it either has no table, or its tables have been optimized
away, or the optimizer detected that the result set is empty.
  
Solution:
Identify the special cases above in the Item_subselect::is_expensive(),
and consider such degenerate subqueries inexpensive.

mysql-test/r/func_group.result

@@ -1837,10 +1837,10 @@ INSERT INTO t2 VALUES
 EXPLAIN EXTENDED
 SELECT MAX(a) FROM t1 WHERE (1,2) IN (SELECT 3,4) AND a<10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	range	a	a	4	NULL	4	100.00	Using where; Using index
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
-Note	1003	select max(`test`.`t1`.`a`) AS `MAX(a)` from `test`.`t1` where (<cache>(<in_optimizer>((1,2),<exists>(select 3,4 having (((1 = 3) or isnull(3)) and ((2 = 4) or isnull(4)) and <is_not_null_test>(3) and <is_not_null_test>(4))))) and (`test`.`t1`.`a` < 10))
+Note	1003	select max(`test`.`t1`.`a`) AS `MAX(a)` from `test`.`t1` where 0
 SELECT MAX(a) FROM t1 WHERE (1,2) IN (SELECT 3,4) AND a<10;
 MAX(a)
 NULL

mysql-test/r/ps_11bugs.result

@@ -120,7 +120,7 @@ create table t1 (a int primary key);
 insert into t1 values (1);
 explain select * from t1 where 3 in (select (1+1) union select 1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	

mysql-test/r/subselect.result

@@ -429,7 +429,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 1 AS `1` from `test`.`t1` where (1 = (select 1 union select 1))
+Note	1003	select 1 AS `1` from `test`.`t1` where 1
 drop table t1;
 CREATE TABLE `t1` (
 `numeropost` mediumint(8) unsigned NOT NULL auto_increment,
@@ -558,10 +558,10 @@ Warnings:
 Note	1003	select max(`test`.`t1`.`numreponse`) AS `MAX(numreponse)` from `test`.`t1` where (`test`.`t1`.`numeropost` = '1')
 EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
 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 where; Using index
+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 `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = '1') and (`test`.`t1`.`numreponse` = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where (`test`.`t1`.`numeropost` = '1'))))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((1 = '1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1371,7 +1371,7 @@ 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	0	0.00	Using where
+1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using where
 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`))

mysql-test/r/subselect4.result

@@ -869,7 +869,7 @@ NULL
 EXPLAIN
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2);
 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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No matching min/max row
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2);
 f1	f2
@@ -960,7 +960,7 @@ NULL
 EXPLAIN
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2);
 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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No matching min/max row
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2);
 f1	f2
@@ -1055,7 +1055,7 @@ NULL
 EXPLAIN
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2 WHERE f3 > 10);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No matching min/max row
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2 WHERE f3 > 10);
 f1	f2
@@ -1146,7 +1146,7 @@ NULL
 EXPLAIN
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2 WHERE f3 > 10);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No matching min/max row
 SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM t2 WHERE f3 > 10);
 f1	f2
@@ -2012,7 +2012,7 @@ FROM t2 JOIN t3 ON t3.f4 = t2.f4
 WHERE t3.f1 = 8
 GROUP BY 1, 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t3	system	NULL	NULL	NULL	NULL	1	Using temporary; Using filesort
+1	PRIMARY	t3	system	NULL	NULL	NULL	NULL	1	Using filesort
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 3	MATERIALIZED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
@@ -2325,5 +2325,19 @@ ORDER BY alias1.b;
 pk	b	pk	b
 1	1	1	1
 drop table t1, t2, t3;
+#
+# MDEV-4144 simple subquery causes full scan instead of range scan
+#
+CREATE TABLE t1 (id int not null auto_increment, x int not null, primary key(id));
+INSERT INTO t1 (x) VALUES (0),(0),(0);
+EXPLAIN
+SELECT x FROM t1 WHERE id > (SELECT MAX(id) - 1000 FROM t1) ORDER BY x LIMIT 1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	PRIMARY	PRIMARY	4	NULL	3	Using where; Using filesort
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+SELECT x FROM t1 WHERE id > (SELECT MAX(id) - 1000 FROM t1) ORDER BY x LIMIT 1;
+x
+0
+drop table t1;
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

mysql-test/r/subselect_innodb.result

@@ -331,7 +331,7 @@ SELECT SUM( c )
 FROM t2
 WHERE (SELECT DISTINCT b FROM t3) > 0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	const	PRIMARY	PRIMARY	4	const	1	Using where; Using index
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 3	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	1	Using temporary
 SELECT *

mysql-test/r/subselect_no_mat.result

@@ -436,7 +436,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 1 AS `1` from `test`.`t1` where (1 = (select 1 union select 1))
+Note	1003	select 1 AS `1` from `test`.`t1` where 1
 drop table t1;
 CREATE TABLE `t1` (
 `numeropost` mediumint(8) unsigned NOT NULL auto_increment,
@@ -565,10 +565,10 @@ Warnings:
 Note	1003	select max(`test`.`t1`.`numreponse`) AS `MAX(numreponse)` from `test`.`t1` where (`test`.`t1`.`numeropost` = '1')
 EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
 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 where; Using index
+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 `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = '1') and (`test`.`t1`.`numreponse` = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where (`test`.`t1`.`numeropost` = '1'))))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((1 = '1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1378,7 +1378,7 @@ 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	0	0.00	Using where
+1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using where
 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`))
@@ -6913,7 +6913,7 @@ INSERT INTO t2 VALUES (1),(2);
 EXPLAIN
 SELECT * FROM t1 WHERE 4 IN (SELECT MAX(b) FROM t2 WHERE EXISTS (SELECT * FROM t1));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 3	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	
 SELECT * FROM t1 WHERE 4 IN (SELECT MAX(b) FROM t2 WHERE EXISTS (SELECT * FROM t1));

mysql-test/r/subselect_no_opts.result

@@ -432,7 +432,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 1 AS `1` from `test`.`t1` where (1 = (select 1 union select 1))
+Note	1003	select 1 AS `1` from `test`.`t1` where 1
 drop table t1;
 CREATE TABLE `t1` (
 `numeropost` mediumint(8) unsigned NOT NULL auto_increment,
@@ -561,10 +561,10 @@ Warnings:
 Note	1003	select max(`test`.`t1`.`numreponse`) AS `MAX(numreponse)` from `test`.`t1` where (`test`.`t1`.`numeropost` = '1')
 EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
 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 where; Using index
+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 `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = '1') and (`test`.`t1`.`numreponse` = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where (`test`.`t1`.`numeropost` = '1'))))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((1 = '1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1374,7 +1374,7 @@ 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	0	0.00	Using where
+1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using where
 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`))

mysql-test/r/subselect_no_scache.result

@@ -435,7 +435,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 1 AS `1` from `test`.`t1` where (1 = (select 1 union select 1))
+Note	1003	select 1 AS `1` from `test`.`t1` where 1
 drop table t1;
 CREATE TABLE `t1` (
 `numeropost` mediumint(8) unsigned NOT NULL auto_increment,
@@ -564,10 +564,10 @@ Warnings:
 Note	1003	select max(`test`.`t1`.`numreponse`) AS `MAX(numreponse)` from `test`.`t1` where (`test`.`t1`.`numeropost` = '1')
 EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
 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 where; Using index
+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 `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = '1') and (`test`.`t1`.`numreponse` = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where (`test`.`t1`.`numeropost` = '1'))))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((1 = '1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1377,7 +1377,7 @@ 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	0	0.00	Using where
+1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using where
 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`))

mysql-test/r/subselect_no_semijoin.result

@@ -432,7 +432,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 1 AS `1` from `test`.`t1` where (1 = (select 1 union select 1))
+Note	1003	select 1 AS `1` from `test`.`t1` where 1
 drop table t1;
 CREATE TABLE `t1` (
 `numeropost` mediumint(8) unsigned NOT NULL auto_increment,
@@ -561,10 +561,10 @@ Warnings:
 Note	1003	select max(`test`.`t1`.`numreponse`) AS `MAX(numreponse)` from `test`.`t1` where (`test`.`t1`.`numeropost` = '1')
 EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
 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 where; Using index
+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 `test`.`t1`.`numreponse` AS `numreponse` from `test`.`t1` where ((`test`.`t1`.`numeropost` = '1') and (`test`.`t1`.`numreponse` = (select max(`test`.`t1`.`numreponse`) from `test`.`t1` where (`test`.`t1`.`numeropost` = '1'))))
+Note	1003	select 3 AS `numreponse` from `test`.`t1` where ((1 = '1'))
 drop table t1;
 CREATE TABLE t1 (a int(1));
 INSERT INTO t1 VALUES (1);
@@ -1374,7 +1374,7 @@ 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	0	0.00	Using where
+1	PRIMARY	t1	ref	salary	salary	5	const	1	100.00	Using where
 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`))

mysql-test/t/subselect4.test

@@ -1865,5 +1865,18 @@ ORDER BY alias1.b;
 
 drop table t1, t2, t3;
 
+--echo #
+--echo # MDEV-4144 simple subquery causes full scan instead of range scan
+--echo #
+
+CREATE TABLE t1 (id int not null auto_increment, x int not null, primary key(id));
+INSERT INTO t1 (x) VALUES (0),(0),(0);
+
+EXPLAIN
+SELECT x FROM t1 WHERE id > (SELECT MAX(id) - 1000 FROM t1) ORDER BY x LIMIT 1;
+SELECT x FROM t1 WHERE id > (SELECT MAX(id) - 1000 FROM t1) ORDER BY x LIMIT 1;
+
+drop table t1;
+
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

sql/item_subselect.cc

@@ -547,8 +547,19 @@ bool Item_subselect::is_expensive()
     if (!cur_join)
       continue;
 
-    /* If a subquery is not optimized we cannot estimate its cost. */
-    if (!cur_join->join_tab)
+    /*
+      Subqueries whose result is known after optimization are not expensive.
+      Such subqueries have all tables optimized away, thus have no join plan.
+    */
+    if (cur_join->optimized &&
+        (cur_join->zero_result_cause || !cur_join->tables_list))
+      return false;
+
+    /*
+      If a subquery is not optimized we cannot estimate its cost. A subquery is
+      considered optimized if it has a join plan.
+    */
+    if (!(cur_join->optimized && cur_join->join_tab))
       return true;
 
     if (sl->first_inner_unit())