MySQL Bugs: #1498: Unimportant mistake in myisam/mi

Bug #1498	Unimportant mistake in myisam/mi_open.c
Submitted:	7 Oct 2003 8:31	Modified:	10 Dec 2003 20:23
Reporter:	Jim Bruin	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: MyISAM storage engine	Severity:	S3 (Non-critical)
Version:	4.0.15a	OS:	Linux (Linux)
Assigned to:	Michael Widenius	CPU Architecture:	Any

Description:
Just a slight difference between mi_state_info_write and mi_state_info_read.  If state->state_diff_length is ever non zero, then these functions will break.

uint mi_state_info_write(File file, MI_STATE_INFO *state, uint pWrite)
{
...
  ptr+=state->state_diff_length;

  for (i=0; i < keys; i++)
  {
    mi_sizestore(ptr,state->key_root[i]);	ptr +=8;
  }
  for (i=0; i < key_blocks; i++)
  {
    mi_sizestore(ptr,state->key_del[i]);	ptr +=8;
  }
...
}

char *mi_state_info_read(char *ptr, MI_STATE_INFO *state)
{
...
  for (i=0; i < keys; i++)
  {
    state->key_root[i]= mi_sizekorr(ptr);	ptr +=8;
  }
  for (i=0; i < key_blocks; i++)
  {
    state->key_del[i] = mi_sizekorr(ptr);	ptr +=8;
  }
  ptr+= state->state_diff_length;
...
}

Its rather unimportant, but figured I would post it anyway.

How to repeat:
Can't think of anything to put here, but it won't let me submit without it.  :)

Suggested fix:
Self explanatory:  Move the "ptr+=state->state_diff_length;" in mi_state_info_read above the for loops.

as far as I see state->state_diff_length is always zero in MySQL.
if it's from pre-MySQL era only Monty can know what is it for.

(and of course, the first word that comes to my mind when I see a dead code in MyISAM is "unireg")

Thank you for your bug report. This issue has been committed to our
source repository of that product and will be incorporated into the
next release.

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Additional info:

Thanks for noticing and reporting this possible problem.

state_diff_length is now always zero but in future MyISAM releases this may not be so. This variable is here to make it easy to later extend the status variable section for some key files and still be able to use the old key files.