Fixed Bug#11226 and reverted fix for Bug#6993.

Using 8 bytes for data pointer does not work at least on
all computers. The result may become 0 or negative number.
(mysqld, myisamchk)
 

myisam/mi_create.c

@@ -194,11 +194,10 @@ int mi_create(const char *name,uint keys,MI_KEYDEF *keydefs,
       test(test_all_bits(options, HA_OPTION_CHECKSUM | HA_PACK_RECORD));
   min_pack_length+=packed;
 
-  if (!ci->data_file_length)
+  if (!ci->data_file_length && ci->max_rows)
   {
-    if (ci->max_rows == 0 || pack_reclength == INT_MAX32)
-      ci->data_file_length= INT_MAX32-1;		/* Should be enough */
-    else if ((~(ulonglong) 0)/ci->max_rows < (ulonglong) pack_reclength)
+    if (pack_reclength == INT_MAX32 ||
+             (~(ulonglong) 0)/ci->max_rows < (ulonglong) pack_reclength)
       ci->data_file_length= ~(ulonglong) 0;
     else
       ci->data_file_length=(ulonglong) ci->max_rows*pack_reclength;

mysql-test/r/variables.result

@@ -482,10 +482,10 @@ t1	CREATE TABLE `t1` (
   `c3` longtext
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
-SET GLOBAL MYISAM_DATA_POINTER_SIZE= 8;
+SET GLOBAL MYISAM_DATA_POINTER_SIZE= 7;
 SHOW VARIABLES LIKE 'MYISAM_DATA_POINTER_SIZE';
 Variable_name	Value
-myisam_data_pointer_size	8
+myisam_data_pointer_size	7
 SET GLOBAL table_cache=-1;
 SHOW VARIABLES LIKE 'table_cache';
 Variable_name	Value

mysql-test/t/variables.test

@@ -363,9 +363,13 @@ drop table t1;
 
 #
 # Bug #6993: myisam_data_pointer_size
+# Wrong bug report, data pointer size must be restricted to 7,
+# setting to 8 will not work on all computers, myisamchk and
+# the server may see a wrong value, such as 0 or negative number
+# if 8 bytes is set.
 #
 
-SET GLOBAL MYISAM_DATA_POINTER_SIZE= 8;
+SET GLOBAL MYISAM_DATA_POINTER_SIZE= 7;
 SHOW VARIABLES LIKE 'MYISAM_DATA_POINTER_SIZE';
 
 #

sql/mysqld.cc

@@ -5153,7 +5153,7 @@ The minimum value for this variable is 4096.",
    "Default pointer size to be used for MyISAM tables.",
    (gptr*) &myisam_data_pointer_size,
    (gptr*) &myisam_data_pointer_size, 0, GET_ULONG, REQUIRED_ARG,
-   4, 2, 8, 0, 1, 0},
+   4, 2, 7, 0, 1, 0},
   {"myisam_max_extra_sort_file_size", OPT_MYISAM_MAX_EXTRA_SORT_FILE_SIZE,
    "Used to help MySQL to decide when to use the slow but safe key cache index create method.",
    (gptr*) &global_system_variables.myisam_max_extra_sort_file_size,