diff --git a/mysql-test/r/ctype_binary.result b/mysql-test/r/ctype_binary.result
index 0e8fe328589..d79265b29c7 100644
--- a/mysql-test/r/ctype_binary.result
+++ b/mysql-test/r/ctype_binary.result
@@ -1425,7 +1425,7 @@ create table t1 as select concat(time_to_sec('10:11:12')) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varbinary(10) NOT NULL DEFAULT ''
+  `c1` varbinary(10) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(extract(year from 20090702)));
diff --git a/mysql-test/r/ctype_cp1251.result b/mysql-test/r/ctype_cp1251.result
index b1e9ff38d26..babed8951a2 100644
--- a/mysql-test/r/ctype_cp1251.result
+++ b/mysql-test/r/ctype_cp1251.result
@@ -1507,7 +1507,7 @@ create table t1 as select concat(time_to_sec('10:11:12')) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(10) CHARACTER SET cp1251 NOT NULL DEFAULT ''
+  `c1` varchar(10) CHARACTER SET cp1251 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(extract(year from 20090702)));
diff --git a/mysql-test/r/ctype_latin1.result b/mysql-test/r/ctype_latin1.result
index 6216819d172..6edddecb88f 100644
--- a/mysql-test/r/ctype_latin1.result
+++ b/mysql-test/r/ctype_latin1.result
@@ -1835,7 +1835,7 @@ create table t1 as select concat(time_to_sec('10:11:12')) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(10) NOT NULL DEFAULT ''
+  `c1` varchar(10) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(extract(year from 20090702)));
diff --git a/mysql-test/r/ctype_ucs.result b/mysql-test/r/ctype_ucs.result
index c2fb90ecfa6..1008f201366 100644
--- a/mysql-test/r/ctype_ucs.result
+++ b/mysql-test/r/ctype_ucs.result
@@ -2667,7 +2667,7 @@ create table t1 as select concat(time_to_sec('10:11:12')) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(10) CHARACTER SET ucs2 NOT NULL DEFAULT ''
+  `c1` varchar(10) CHARACTER SET ucs2 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(extract(year from 20090702)));
diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index e14b54b59a3..122d722be71 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -3511,7 +3511,7 @@ create table t1 as select concat(time_to_sec('10:11:12')) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(10) CHARACTER SET utf8 NOT NULL DEFAULT ''
+  `c1` varchar(10) CHARACTER SET utf8 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(extract(year from 20090702)));
diff --git a/mysql-test/r/func_time.result b/mysql-test/r/func_time.result
index f1b2196ebfa..0ed46ba270b 100644
--- a/mysql-test/r/func_time.result
+++ b/mysql-test/r/func_time.result
@@ -1315,6 +1315,20 @@ SELECT 1 FROM t1 ORDER BY @x:=makedate(a,a);
 1
 1
 DROP TABLE t1;
+#
+# Bug #52160: crash and inconsistent results when grouping
+#             by a function and column
+#
+CREATE TABLE t1(a CHAR(10) NOT NULL);
+INSERT INTO t1 VALUES (''),('');
+SELECT COUNT(*) FROM t1 GROUP BY TIME_TO_SEC(a);
+COUNT(*)
+2
+Warnings:
+Warning	1292	Truncated incorrect time value: ''
+Warning	1292	Truncated incorrect time value: ''
+Warning	1292	Truncated incorrect time value: ''
+DROP TABLE t1;
 End of 5.1 tests
 #
 # Bug#57039: constant subtime expression returns incorrect result.
diff --git a/mysql-test/r/type_blob.result b/mysql-test/r/type_blob.result
index 78f31286ea7..e3363fcabf9 100644
--- a/mysql-test/r/type_blob.result
+++ b/mysql-test/r/type_blob.result
@@ -975,4 +975,14 @@ SELECT LENGTH(c) FROM t2;
 LENGTH(c)
 65535
 DROP TABLE t1, t2;
+# Bug #52160: crash and inconsistent results when grouping
+#             by a function and column
+CREATE FUNCTION f1() RETURNS TINYBLOB RETURN 1;
+CREATE TABLE t1(a CHAR(1));
+INSERT INTO t1 VALUES ('0'), ('0');
+SELECT COUNT(*) FROM t1 GROUP BY f1(), a;
+COUNT(*)
+2
+DROP FUNCTION f1;
+DROP TABLE t1;
 End of 5.1 tests
diff --git a/mysql-test/t/func_time.test b/mysql-test/t/func_time.test
index 08c09adb093..0a2b473ca59 100644
--- a/mysql-test/t/func_time.test
+++ b/mysql-test/t/func_time.test
@@ -832,6 +832,16 @@ INSERT INTO t1 VALUES (0),(9.216e-096);
 SELECT 1 FROM t1 ORDER BY @x:=makedate(a,a);
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #52160: crash and inconsistent results when grouping
+--echo #             by a function and column
+--echo #
+
+CREATE TABLE t1(a CHAR(10) NOT NULL);
+INSERT INTO t1 VALUES (''),('');
+SELECT COUNT(*) FROM t1 GROUP BY TIME_TO_SEC(a);
+DROP TABLE t1;
+
 --echo End of 5.1 tests
 
 --echo #
diff --git a/mysql-test/t/type_blob.test b/mysql-test/t/type_blob.test
index c06d8ac97e0..fa67afa48e8 100644
--- a/mysql-test/t/type_blob.test
+++ b/mysql-test/t/type_blob.test
@@ -617,4 +617,17 @@ SELECT LENGTH(c) FROM t2;
 
 DROP TABLE t1, t2;
 
+--echo # Bug #52160: crash and inconsistent results when grouping
+--echo #             by a function and column
+
+CREATE FUNCTION f1() RETURNS TINYBLOB RETURN 1;
+
+CREATE TABLE t1(a CHAR(1));
+INSERT INTO t1 VALUES ('0'), ('0');
+
+SELECT COUNT(*) FROM t1 GROUP BY f1(), a;
+
+DROP FUNCTION f1;
+DROP TABLE t1;
+
 --echo End of 5.1 tests
diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index 004eb83cbeb..72a5aa0c296 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -361,6 +361,7 @@ public:
   const char *func_name() const { return "time_to_sec"; }
   void fix_length_and_dec()
   {
+    maybe_null= TRUE;
     decimals=0;
     max_length=10*MY_CHARSET_BIN_MB_MAXLEN;
   }
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 2a2fe3eb36f..d521abd51a3 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -15218,6 +15218,8 @@ calc_group_buffer(JOIN *join,ORDER *group)
         {
           key_length+= 8;
         }
+        else if (type == MYSQL_TYPE_BLOB)
+          key_length+= MAX_BLOB_WIDTH;		// Can't be used as a key
         else
         {
           /*