bk commit into 5.1 tree (istruewing:1.2555) BUG#29838

[Ingo Struewing]

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ChangeSet@stripped, 2007-07-28 19:01:19+02:00, istruewing@stripped +1 -0
  Bug#29838 - myisam corruption using concurrent select ... and update
  
  When using concurrent insert with parallel index reads, it could
  happen that reading sessions found keys that pointed to records
  yet to be written to the data file. The result was a report of
  a corrupted table. But it was false alert.
  
  When inserting a record in a table with indexes, the keys are
  inserted into the indexes before the record is written to the data
  file. When the insert happens concurrently to selects, an
  index read can find a key that references the record that is not
  yet written to the data file. To avoid any access to such record,
  the select saves the current end of file position when it starts.
  Since concurrent inserts are always appended at end of the data
  file, the select can easily ignore any concurrently inserted record.
  
  The problem was that the ignore was only done for non-exact key
  searches (partial key or using >, >=, < or <=).
  
  The fix is to ignore concurrently inserted records also for
  exact key searches.
  
  No test case. Concurrent inserts cannot be tested with the test
  suite. Test cases are attached to the bug report.
  
  The fix shall go to 4.1 and up when approved.

  storage/myisam/mi_rkey.c@stripped, 2007-07-28 19:01:15+02:00, istruewing@stripped +48
-33
    Bug#29838 - myisam corruption using concurrent select ... and update
    Fixed mi_rkey() to always ignore records beyond saved eof.

diff -Nrup a/storage/myisam/mi_rkey.c b/storage/myisam/mi_rkey.c
--- a/storage/myisam/mi_rkey.c	2007-05-10 11:59:32 +02:00
+++ b/storage/myisam/mi_rkey.c	2007-07-28 19:01:15 +02:00
@@ -93,43 +93,58 @@ int mi_rkey(MI_INFO *info, uchar *buf, i
     if (!_mi_search(info, keyinfo, key_buff, use_key_length,
                     myisam_read_vec[search_flag], info->s->state.key_root[inx]))
     {
-      /*
-        If we searching for a partial key (or using >, >=, < or <=) and
-        the data is outside of the data file, we need to continue searching
-        for the first key inside the data file
-      */
-      if (info->lastpos >= info->state->data_file_length &&
-          (search_flag != HA_READ_KEY_EXACT ||
-           last_used_keyseg != keyinfo->seg + keyinfo->keysegs))
+      if (info->lastpos >= info->state->data_file_length)
       {
-        do
+        /*
+          If we searching for a partial key (or using >, >=, < or <=) and
+          the data is outside of the data file, we need to continue searching
+          for the first key inside the data file
+        */
+        if (search_flag != HA_READ_KEY_EXACT ||
+            last_used_keyseg != keyinfo->seg + keyinfo->keysegs)
+        {
+          do
+          {
+            uint not_used[2];
+            /*
+              Skip rows that are inserted by other threads since we got a lock
+              Note that this can only happen if we are not searching after an
+              full length exact key, because the keys are sorted
+              according to position
+            */
+            if  (_mi_search_next(info, keyinfo, info->lastkey,
+                                 info->lastkey_length,
+                                 myisam_readnext_vec[search_flag],
+                                 info->s->state.key_root[inx]))
+              break; /* purecov: inspected */
+            /*
+              Check that the found key does still match the search.
+              _mi_search_next() delivers the next key regardless of its
+              value.
+            */
+            if (search_flag == HA_READ_KEY_EXACT &&
+                ha_key_cmp(keyinfo->seg, key_buff, info->lastkey,
+                           use_key_length, SEARCH_FIND, not_used))
+            {
+              /* purecov: begin inspected */
+              my_errno= HA_ERR_KEY_NOT_FOUND;
+              info->lastpos= HA_OFFSET_ERROR;
+              break;
+              /* purecov: end */
+            }
+          } while (info->lastpos >= info->state->data_file_length);
+        }
+        else
         {
-          uint not_used[2];
-          /*
-            Skip rows that are inserted by other threads since we got a lock
-            Note that this can only happen if we are not searching after an
-            full length exact key, because the keys are sorted
-            according to position
-          */
-          if  (_mi_search_next(info, keyinfo, info->lastkey,
-                               info->lastkey_length,
-                               myisam_readnext_vec[search_flag],
-                               info->s->state.key_root[inx]))
-            break;
           /*
-            Check that the found key does still match the search.
-            _mi_search_next() delivers the next key regardless of its
-            value.
+            We cannot use rows that are inserted by other threads since
+            we got a lock ("concurrent inserts"). The record may not
+            even be present yet. Keys are inserted before the record is.
+            (Bug #29838)
           */
-          if (search_flag == HA_READ_KEY_EXACT &&
-              ha_key_cmp(keyinfo->seg, key_buff, info->lastkey, use_key_length,
-                         SEARCH_FIND, not_used))
-          {
-            my_errno= HA_ERR_KEY_NOT_FOUND;
-            info->lastpos= HA_OFFSET_ERROR;
-            break;
-          }
-        } while (info->lastpos >= info->state->data_file_length);
+          my_errno= HA_ERR_KEY_NOT_FOUND;
+          info->lastpos= HA_OFFSET_ERROR;
+        }
       }
     }
   }