4 files changed, 110 insertions, 3 deletions
diff --git a/mysql-test/r/func_time.result b/mysql-test/r/func_time.result
index e03de2ca582..477a6a4041a 100644
--- a/mysql-test/r/func_time.result
+++ b/mysql-test/r/func_time.result
@@ -3402,3 +3402,61 @@ CAST(LAST_DAY(TIME'00:00:00') AS TIME) AS c3;
 c1	c2	c3
 2018-02-28	00:00:00	00:00:00
 SET TIMESTAMP=DEFAULT;
+#
+# MDEV-15702 Remove the use of STRING_ITEM from Item_func_date_format::fix_length_and_dec()
+#
+SELECT DATE_FORMAT('2001-01-01',POINT(1,1));
+ERROR HY000: Illegal parameter data type geometry for operation 'date_format'
+SELECT DATE_FORMAT(POINT(1,1),'10');
+ERROR HY000: Illegal parameter data type geometry for operation 'date_format'
+SELECT DATE_FORMAT('2001-01-01',ROW(1,1));
+ERROR HY000: Illegal parameter data type row for operation 'date_format'
+SELECT DATE_FORMAT(ROW(1,1),'10');
+ERROR HY000: Illegal parameter data type row for operation 'date_format'
+SELECT DATE_FORMAT('2001-01-01','%Y',POINT(1,1));
+ERROR HY000: Illegal parameter data type geometry for operation 'date_format'
+SELECT DATE_FORMAT('2001-01-01','%Y',ROW(1,1));
+ERROR HY000: Illegal parameter data type row for operation 'date_format'
+SELECT DATE_FORMAT('2001-01-01','%Y',@unknown_user_variable);
+DATE_FORMAT('2001-01-01','%Y',@unknown_user_variable)
+2001
+Warnings:
+Warning	1649	Unknown locale: 'NULL'
+CREATE TABLE t1 AS SELECT
+DATE_FORMAT('2001-01-01',NULL) AS c0,
+DATE_FORMAT('2001-01-01','10') AS c1,
+DATE_FORMAT('2001-01-01',10) AS c2,
+DATE_FORMAT('2001-01-01',10.0) AS c3,
+DATE_FORMAT('2001-01-01',10e0) AS c4,
+DATE_FORMAT('2001-01-01',TIME'10:20:30') AS c5;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c0` char(0) DEFAULT NULL,
+  `c1` varchar(2) DEFAULT NULL,
+  `c2` varchar(2) DEFAULT NULL,
+  `c3` varchar(4) DEFAULT NULL,
+  `c4` varchar(2) DEFAULT NULL,
+  `c5` varchar(8) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1;
+EXECUTE IMMEDIATE
+"CREATE TABLE t1 AS SELECT
+   DATE_FORMAT('2001-01-01',?) AS c0,
+   DATE_FORMAT('2001-01-01',?) AS c1,
+   DATE_FORMAT('2001-01-01',?) AS c2,
+   DATE_FORMAT('2001-01-01',?) AS c3,
+   DATE_FORMAT('2001-01-01',?) AS c4,
+   DATE_FORMAT('2001-01-01',?) AS c5"
+USING NULL, '10', 10, 10.0, 10e0, TIME'10:20:30';
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c0` char(0) DEFAULT NULL,
+  `c1` varchar(2) DEFAULT NULL,
+  `c2` varchar(2) DEFAULT NULL,
+  `c3` varchar(4) DEFAULT NULL,
+  `c4` varchar(2) DEFAULT NULL,
+  `c5` varchar(100) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1;
diff --git a/mysql-test/t/func_time.test b/mysql-test/t/func_time.test
index a475c33b925..ad81a336544 100644
--- a/mysql-test/t/func_time.test
+++ b/mysql-test/t/func_time.test
@@ -1998,3 +1998,46 @@ SELECT
   CAST(CAST(LAST_DAY(TIME'00:00:00') AS DATE) AS TIME) AS c2,
   CAST(LAST_DAY(TIME'00:00:00') AS TIME) AS c3;
 SET TIMESTAMP=DEFAULT;
+
+
+--echo #
+--echo # MDEV-15702 Remove the use of STRING_ITEM from Item_func_date_format::fix_length_and_dec()
+--echo #
+
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT('2001-01-01',POINT(1,1));
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT(POINT(1,1),'10');
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT('2001-01-01',ROW(1,1));
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT(ROW(1,1),'10');
+
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT('2001-01-01','%Y',POINT(1,1));
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT DATE_FORMAT('2001-01-01','%Y',ROW(1,1));
+
+SELECT DATE_FORMAT('2001-01-01','%Y',@unknown_user_variable);
+
+CREATE TABLE t1 AS SELECT
+  DATE_FORMAT('2001-01-01',NULL) AS c0,
+  DATE_FORMAT('2001-01-01','10') AS c1,
+  DATE_FORMAT('2001-01-01',10) AS c2,
+  DATE_FORMAT('2001-01-01',10.0) AS c3,
+  DATE_FORMAT('2001-01-01',10e0) AS c4,
+  DATE_FORMAT('2001-01-01',TIME'10:20:30') AS c5;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+EXECUTE IMMEDIATE
+"CREATE TABLE t1 AS SELECT
+   DATE_FORMAT('2001-01-01',?) AS c0,
+   DATE_FORMAT('2001-01-01',?) AS c1,
+   DATE_FORMAT('2001-01-01',?) AS c2,
+   DATE_FORMAT('2001-01-01',?) AS c3,
+   DATE_FORMAT('2001-01-01',?) AS c4,
+   DATE_FORMAT('2001-01-01',?) AS c5"
+USING NULL, '10', 10, 10.0, 10e0, TIME'10:20:30';
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index 4ddeb83b163..f612b4d6aa2 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -1859,11 +1859,12 @@ void Item_func_date_format::fix_length_and_dec()
   if (!thd->variables.lc_time_names->is_ascii)
     repertoire|= MY_REPERTOIRE_EXTENDED;
   collation.set(cs, arg1->collation.derivation, repertoire);
-  if (arg1->type() == STRING_ITEM)
+  StringBuffer<STRING_BUFFER_USUAL_SIZE> buffer;
+  String *str;
+  if (args[1]->basic_const_item() && (str= args[1]->val_str(&buffer)))
   {						// Optimize the normal case
     fixed_length=1;
-    max_length= format_length(arg1->val_str(NULL)) *
-                collation.collation->mbmaxlen;
+    max_length= format_length(str) * collation.collation->mbmaxlen;
   }
   else
   {
diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index c3bda9d85ba..30d5018ff36 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -847,6 +847,11 @@ public:
 
 class Item_func_date_format :public Item_str_func
 {
+  bool check_arguments() const
+  {
+    return args[0]->check_type_can_return_date(func_name()) ||
+           check_argument_types_can_return_text(1, arg_count);
+  }
   const MY_LOCALE *locale;
   int fixed_length;
   String value;