Merge chilla.local:/home/mydev/mysql-4.1-bug29838

into  chilla.local:/home/mydev/mysql-5.0-bug29838

myisam/mi_rkey.c

@@ -95,45 +95,66 @@ int mi_rkey(MI_INFO *info, byte *buf, int inx, const byte *key, uint key_len,
                     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
+        Found a key, but it might not be usable. We cannot use rows that
+        are inserted by other threads after we got our table lock
+        ("concurrent inserts"). The record may not even be present yet.
+        Keys are inserted into the index(es) before the record is
+        inserted into the data file. When we got our table lock, we
+        saved the current data_file_length. Concurrent inserts always go
+        to the end of the file. So we can test if the found key
+        references a new record.
       */
-      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)
       {
+        /* The key references a concurrently inserted record. */
+        if (search_flag == HA_READ_KEY_EXACT &&
+            last_used_keyseg == keyinfo->seg + keyinfo->keysegs)
+        {
+          /* Simply ignore the key if it matches exactly. (Bug #29838) */
+          my_errno= HA_ERR_KEY_NOT_FOUND;
+          info->lastpos= HA_OFFSET_ERROR;
+        }
+        else
+        {
+          /*
+            If 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.
+          */
           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
+              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 a 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;
+              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))
+                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);
         }
       }
     }
+  }
   if (share->concurrent_insert)
     rw_unlock(&share->key_root_lock[inx]);