Fix for BUG#4785:

 * myisampack leaves key_file_length value from original table
 * myisamchk uses this value when calculating key file pointer length

include/myisam.h

@@ -96,6 +96,7 @@ typedef struct st_mi_create_info
   ha_rows reloc_rows;
   ulonglong auto_increment;
   ulonglong data_file_length;
+  ulonglong key_file_length;
   uint raid_type,raid_chunks;
   ulong raid_chunksize;
   uint old_options;

myisam/mi_check.c

@@ -3520,7 +3520,7 @@ int recreate_table(MI_CHECK *param, MI_INFO **org_info, char *filename)
   create_info.raid_chunksize= share.base.raid_chunksize;
   create_info.language = (param->language ? param->language :
 			  share.state.header.language);
-
+  create_info.key_file_length=  status_info.key_file_length;
   /* We don't have to handle symlinks here because we are using
      HA_DONT_TOUCH_DATA */
   if (mi_create(filename,

myisam/mi_create.c

@@ -46,7 +46,7 @@ int mi_create(const char *name,uint keys,MI_KEYDEF *keydefs,
   ulong reclength, real_reclength,min_pack_length;
   char filename[FN_REFLEN],linkname[FN_REFLEN], *linkname_ptr;
   ulong pack_reclength;
-  ulonglong tot_length,max_rows;
+  ulonglong tot_length,max_rows, tmp;
   enum en_fieldtype type;
   MYISAM_SHARE share;
   MI_KEYDEF *keydef,tmp_keydef;
@@ -442,10 +442,15 @@ int mi_create(const char *name,uint keys,MI_KEYDEF *keydefs,
   share.state.auto_increment=ci->auto_increment;
   share.options=options;
   share.base.rec_reflength=pointer;
+  /* Get estimate for index file length (this may be wrong for FT keys) */
+  tmp= (tot_length + max_key_block_length * keys *
+	MI_INDEX_BLOCK_MARGIN) / MI_MIN_KEY_BLOCK_LENGTH;
+  /*
+    use maximum of key_file_length we calculated and key_file_length value we
+    got from MYI file header (see also myisampack.c:save_state)
+  */
   share.base.key_reflength=
-    mi_get_pointer_length((tot_length + max_key_block_length * keys *
-			   MI_INDEX_BLOCK_MARGIN) / MI_MIN_KEY_BLOCK_LENGTH,
-			  3);
+    mi_get_pointer_length(max(ci->key_file_length,tmp),3);
   share.base.keys= share.state.header.keys = keys;
   share.state.header.uniques= uniques;
   mi_int2store(share.state.header.key_parts,key_segs);

myisam/myisampack.c

@@ -2041,7 +2041,11 @@ static int save_state(MI_INFO *isam_file,PACK_MRG_INFO *mrg,my_off_t new_length,
   share->state.split=(ha_rows) mrg->records;
   share->state.version=(ulong) time((time_t*) 0);
   share->state.key_map=0;
-  share->state.state.key_file_length=share->base.keystart;
+  /*
+    Don't save key_file_length here, keep key_file_length of original file
+    so "myisamchk -rq" can use this value (this is necessary because index 
+    size cannot be easily calculated for fulltext keys)
+  */
   for (key=0 ; key < share->base.keys ; key++)
     share->state.key_root[key]= HA_OFFSET_ERROR;
   for (key=0 ; key < share->state.header.max_block_size ; key++)