Bug #52160: crash and inconsistent results when grouping

            by a function and column

The bugreport reveals two different bugs about grouping
on a function:

1) grouping by the TIME_TO_SEC function result caused
   a server crash or wrong results and
2) grouping by the function returning a blob caused
   an unexpected "Duplicate entry" error and wrong
   result.

Details for the 1st bug:

TIME_TO_SEC() returns NULL if its argument is invalid (empty
string for example). Thus its nullability depends not only
on the nullability of its arguments but also on their values.
Fixed by (overoptimistically) setting TIME_TO_SEC() to be
nullable despite the nullability of its arguments.

Details for the 2nd bug:

The server is unable to create indices on blobs without
explicit blob key part length. However, this fact was
ignored for blob function result fields of GROUP BY
intermediate tables.
Fixed by disabling GROUP BY index creation for blob
function result fields like regular blob fields.

mysql-test/r/func_time.result

@@ -1343,4 +1343,18 @@ 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

mysql-test/r/type_blob.result

@@ -974,3 +974,14 @@ ERROR 42000: Display width out of range for column 'cast as char' (max = 4294967
 explain select convert(1, binary(999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999));
 ERROR 42000: Display width out of range for column 'cast as char' (max = 4294967295)
 End of 5.0 tests
+# 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

mysql-test/t/func_time.test

@@ -849,4 +849,14 @@ 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

mysql-test/t/type_blob.test

@@ -612,3 +612,19 @@ explain select convert(1, binary(4294967296));
 explain select convert(1, binary(999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999));
 
 --echo End of 5.0 tests
+
+--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
+

sql/item_timefunc.h

@@ -331,6 +331,7 @@ 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;
   }

sql/sql_select.cc

@@ -15198,6 +15198,8 @@ 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
         {
           /*