Fixed bug mdev-5468.

The field JOIN::select_lex->where should be updated after the call
of remove_eq_conds() in the function make_join_statistics(). This
matters for subselects.

mysql-test/r/subselect4.result

@@ -2348,5 +2348,32 @@ SELECT * FROM t1 AS t
 WHERE a='r' AND (c,b) NOT IN (SELECT c,b FROM t2 WHERE (c,b)=(t.c,t.b));
 a	b	c	d
 DROP TABLE t1, t2;
+#
+# MDEV-5468: assertion failure with a simplified condition in subselect
+#
+CREATE TABLE t1 (a int, b int) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,1);
+CREATE TABLE t2 ( pk int PRIMARY KEY, c INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1,4), (2,6);
+SELECT ( SELECT MAX(b) FROM t1, t2 WHERE pk = a AND b < from_sq.c ) AS select_sq,
+COUNT( DISTINCT from_sq.c ) 
+FROM ( SELECT DISTINCT t2_1.* FROM t2 AS t2_1, t2 AS t2_2 ) AS from_sq
+GROUP BY select_sq ;
+select_sq	COUNT( DISTINCT from_sq.c )
+1	2
+DROP TABLE t1,t2;
+CREATE TABLE t1 (id int, a2 char(2), a3 char(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,'BE','BEL');
+CREATE TABLE t2 (id int, a2 char(2), a3 char(3)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1,'BE','BEL'), (2,'MX','MEX');
+CREATE VIEW v2 AS SELECT DISTINCT * FROM t2;
+SELECT * FROM t1 AS outer_t1, v2  
+WHERE v2.a3 = outer_t1.a3 
+AND EXISTS ( SELECT * FROM t1 WHERE a2 < v2.a2 AND id = outer_t1.id )
+AND outer_t1.a3 < 'J'    
+ORDER BY v2.id;
+id	a2	a3	id	a2	a3
+DROP VIEW v2;
+DROP TABLE t1,t2;
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

mysql-test/t/subselect4.test

@@ -1936,5 +1936,39 @@ SELECT * FROM t1 AS t
 
 DROP TABLE t1, t2;
 
+--echo #
+--echo # MDEV-5468: assertion failure with a simplified condition in subselect
+--echo #
+
+CREATE TABLE t1 (a int, b int) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,1);
+
+CREATE TABLE t2 ( pk int PRIMARY KEY, c INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1,4), (2,6);
+
+SELECT ( SELECT MAX(b) FROM t1, t2 WHERE pk = a AND b < from_sq.c ) AS select_sq,
+       COUNT( DISTINCT from_sq.c ) 
+FROM ( SELECT DISTINCT t2_1.* FROM t2 AS t2_1, t2 AS t2_2 ) AS from_sq
+GROUP BY select_sq ;
+
+DROP TABLE t1,t2;
+
+
+CREATE TABLE t1 (id int, a2 char(2), a3 char(3)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (1,'BE','BEL');
+
+CREATE TABLE t2 (id int, a2 char(2), a3 char(3)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1,'BE','BEL'), (2,'MX','MEX');
+CREATE VIEW v2 AS SELECT DISTINCT * FROM t2;
+
+SELECT * FROM t1 AS outer_t1, v2  
+WHERE v2.a3 = outer_t1.a3 
+      AND EXISTS ( SELECT * FROM t1 WHERE a2 < v2.a2 AND id = outer_t1.id )
+      AND outer_t1.a3 < 'J'    
+ORDER BY v2.id;
+
+DROP VIEW v2;
+DROP TABLE t1,t2;
+
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

sql/sql_select.cc

@@ -3535,6 +3535,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
   if (conds && const_count)
   { 
     conds= remove_eq_conds(join->thd, conds, &join->cond_value);
+    join->select_lex->where= conds;
     if (join->cond_value == Item::COND_FALSE)
     {
       join->impossible_where= true;