func_str.test:

  Added test cases for bug #11469.
item_strfunc.h:
  Fixed bug #11469: wrong implementation of the not_null_tables
  method for CONCAT_WS.

mysql-test/r/func_str.result

@@ -800,3 +800,53 @@ SELECT * FROM t1, t2 WHERE num=substring(str from 1 for 6);
 str	num
 notnumber	0
 DROP TABLE t1,t2;
+CREATE TABLE t1(
+id int(11) NOT NULL auto_increment,
+pc int(11) NOT NULL default '0',
+title varchar(20) default NULL,
+PRIMARY KEY (id)
+);
+INSERT INTO t1 VALUES
+(1, 0, 'Main'),
+(2, 1, 'Toys'),
+(3, 1, 'Games');
+SELECT t1.id, CONCAT_WS('->', t3.title, t2.title, t1.title) as col1
+FROM t1 LEFT JOIN t1 AS t2 ON t1.pc=t2.id
+LEFT JOIN t1 AS t3 ON t2.pc=t3.id;
+id	col1
+1	Main
+2	Main->Toys
+3	Main->Games
+SELECT t1.id, CONCAT_WS('->', t3.title, t2.title, t1.title) as col1
+FROM t1 LEFT JOIN t1 AS t2 ON t1.pc=t2.id
+LEFT JOIN t1 AS t3 ON t2.pc=t3.id
+WHERE CONCAT_WS('->', t3.title, t2.title, t1.title) LIKE '%Toys%';
+id	col1
+2	Main->Toys
+DROP TABLE t1;
+CREATE TABLE t1(
+trackid     int(10) unsigned NOT NULL auto_increment,
+trackname   varchar(100) NOT NULL default '',
+PRIMARY KEY (trackid)
+);
+CREATE TABLE t2(
+artistid    int(10) unsigned NOT NULL auto_increment,
+artistname  varchar(100) NOT NULL default '',
+PRIMARY KEY (artistid)
+);
+CREATE TABLE t3(
+trackid     int(10) unsigned NOT NULL,
+artistid    int(10) unsigned NOT NULL,
+PRIMARY KEY (trackid,artistid)
+);
+INSERT INTO t1 VALUES (1, 'April In Paris'), (2, 'Autumn In New York');
+INSERT INTO t2 VALUES (1, 'Vernon Duke');
+INSERT INTO t3 VALUES (1,1);
+SELECT CONCAT_WS(' ', trackname, artistname) trackname, artistname
+FROM t1 LEFT JOIN t3 ON t1.trackid=t3.trackid
+LEFT JOIN t2 ON t2.artistid=t3.artistid
+WHERE CONCAT_WS(' ', trackname, artistname) LIKE '%In%';
+trackname	artistname
+April In Paris Vernon Duke	Vernon Duke
+Autumn In New York	NULL
+DROP TABLE t1,t2,t3;

mysql-test/t/func_str.test

@@ -541,3 +541,59 @@ SELECT * FROM t1, t2 WHERE num=str;
 SELECT * FROM t1, t2 WHERE num=substring(str from 1 for 6);
 
 DROP TABLE t1,t2;
+
+#
+# Bug #11469: NOT NULL optimization wrongly used for arguments of CONCAT_WS  
+#
+
+CREATE TABLE t1(
+  id int(11) NOT NULL auto_increment,
+  pc int(11) NOT NULL default '0',
+  title varchar(20) default NULL,
+  PRIMARY KEY (id)
+);
+
+INSERT INTO t1 VALUES
+  (1, 0, 'Main'),
+  (2, 1, 'Toys'),
+  (3, 1, 'Games');
+
+SELECT t1.id, CONCAT_WS('->', t3.title, t2.title, t1.title) as col1
+  FROM t1 LEFT JOIN t1 AS t2 ON t1.pc=t2.id
+          LEFT JOIN t1 AS t3 ON t2.pc=t3.id;
+SELECT t1.id, CONCAT_WS('->', t3.title, t2.title, t1.title) as col1
+  FROM t1 LEFT JOIN t1 AS t2 ON t1.pc=t2.id
+          LEFT JOIN t1 AS t3 ON t2.pc=t3.id
+    WHERE CONCAT_WS('->', t3.title, t2.title, t1.title) LIKE '%Toys%';
+
+DROP TABLE t1;
+
+
+CREATE TABLE t1(
+  trackid     int(10) unsigned NOT NULL auto_increment,
+  trackname   varchar(100) NOT NULL default '',
+  PRIMARY KEY (trackid)
+);
+
+CREATE TABLE t2(
+  artistid    int(10) unsigned NOT NULL auto_increment,
+  artistname  varchar(100) NOT NULL default '',
+  PRIMARY KEY (artistid)
+);
+
+CREATE TABLE t3(
+  trackid     int(10) unsigned NOT NULL,
+  artistid    int(10) unsigned NOT NULL,
+  PRIMARY KEY (trackid,artistid)
+);
+
+INSERT INTO t1 VALUES (1, 'April In Paris'), (2, 'Autumn In New York');
+INSERT INTO t2 VALUES (1, 'Vernon Duke');
+INSERT INTO t3 VALUES (1,1);
+
+SELECT CONCAT_WS(' ', trackname, artistname) trackname, artistname
+  FROM t1 LEFT JOIN t3 ON t1.trackid=t3.trackid
+          LEFT JOIN t2 ON t2.artistid=t3.artistid
+    WHERE CONCAT_WS(' ', trackname, artistname) LIKE '%In%';
+
+DROP TABLE t1,t2,t3;

sql/item_strfunc.h

@@ -95,6 +95,7 @@ public:
   String *val_str(String *);
   void fix_length_and_dec();
   const char *func_name() const { return "concat_ws"; }
+  table_map not_null_tables() const { return 0; }
 };
 
 class Item_func_reverse :public Item_str_func