bk commit into 5.0 tree (svoj:1.2439) BUG#27516

[Sergey Vojtovich]

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ChangeSet@stripped, 2007-04-13 12:38:27+05:00, svoj@stripped +1 -0
  BUG#27516 - divide by zero crash during optimize table
  
  When a table status is requested by statement like SHOW TABLE
  STATUS and there is another statement (e.g. DELETE) sets
  number of records to 0 concurrently, we may get division by
  zero error, which crashes a server.
  
  This is fixed by using thread local variable x->records instead
  of shared info->state->records when we check if it is zero and
  divide by it.

  myisam/mi_info.c@stripped, 2007-04-13 12:38:26+05:00, svoj@stripped +3 -3
    Information schema does not lock a table when it requests table
    state info. If another thread sets info->state->records to 0
    after we check if it is 0 and before we divide by it we may get
    division by zero error.
    
    Check and divide by local x->records variable instead of shared
    info->state->records.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	svoj
# Host:	june.mysql.com
# Root:	/home/svoj/devel/mysql/BUG27516/mysql-5.0-engines

--- 1.17/myisam/mi_info.c	2006-12-31 00:02:04 +04:00
+++ 1.18/myisam/mi_info.c	2007-04-13 12:38:26 +05:00
@@ -57,9 +57,9 @@ int mi_status(MI_INFO *info, register MI
 
     x->keys	 	= share->state.header.keys;
     x->check_time	= share->state.check_time;
-    x->mean_reclength	= info->state->records ?
-      (ulong) ((info->state->data_file_length-info->state->empty)/
-	       info->state->records) : (ulong) share->min_pack_length;
+    x->mean_reclength= x->records ?
+      (ulong) ((x->data_file_length - x->delete_length) / x->records) :
+      (ulong) share->min_pack_length;
   }
   if (flag & HA_STATUS_ERRKEY)
   {