BUG#40827 - Killing insert-select to MyISAM can cause table corruption

                  
Killing insert-select statement on MyISAM corrupts the table.
                  
Killing the insert-select statement corrupts the MyISAM table only
when the destination table is empty and when it has indexes. When 
we bulk insert huge data and if the destination table is empty we 
disable the indexes for fast inserts, data is then inserted and 
indexes are re-enabled after bulk_insert operation
                  
Killing the query, aborts the repair table operation during enable
indexes phase leading to table corruption.
                
We now truncate the table when we detect that enable indexes is
killed for bulk insert query.As we have an empty table before the 
operation, we can fix by truncating the table.

mysql-test/r/myisam.result:
  Result file for BUG#40827
mysql-test/t/myisam.test:
  Testcase for BUG#40827
storage/myisam/ha_myisam.cc:
  Fixed end_bulk_insert() method to truncate the table when we detect enable 
  index operation is killed.

1 files changed, 49 insertions, 4 deletions

diff --git a/storage/myisam/ha_myisam.cc b/storage/myisam/ha_myisam.cc
index dd66c255475..b98b090d021 100644
--- a/storage/myisam/ha_myisam.cc
+++ b/storage/myisam/ha_myisam.cc
@@ -43,6 +43,28 @@ TYPELIB myisam_stats_method_typelib= {
   array_elements(myisam_stats_method_names) - 1, "",
   myisam_stats_method_names, NULL};
 
+#ifndef DBUG_OFF
+/**
+  Causes the thread to wait in a spin lock for a query kill signal.
+  This function is used by the test frame work to identify race conditions.
+
+  The signal is caught and ignored and the thread is not killed.
+*/
+
+static void debug_wait_for_kill(const char *info)
+{
+  DBUG_ENTER("debug_wait_for_kill");
+  const char *prev_info;
+  THD *thd;
+  thd= current_thd;
+  prev_info= thd_proc_info(thd, info);
+  while(!thd->killed)
+    my_sleep(1000);
+  DBUG_PRINT("info", ("Exit debug_wait_for_kill"));
+  thd_proc_info(thd, prev_info);
+  DBUG_VOID_RETURN;
+}
+#endif
 
 /*****************************************************************************
 ** MyISAM tables
@@ -1395,6 +1417,9 @@ int ha_myisam::enable_indexes(uint mode)
 {
   int error;
 
+  DBUG_EXECUTE_IF("wait_in_enable_indexes",
+                  debug_wait_for_kill("wait_in_enable_indexes"); );
+
   if (mi_is_all_keys_active(file->s->state.key_map, file->s->base.keys))
   {
     /* All indexes are enabled already. */
@@ -1508,8 +1533,9 @@ void ha_myisam::start_bulk_insert(ha_rows rows)
     /*
       Only disable old index if the table was empty and we are inserting
       a lot of rows.
-      We should not do this for only a few rows as this is slower and
-      we don't want to update the key statistics based of only a few rows.
+      Note that in end_bulk_insert() we may truncate the table if
+      enable_indexes() failed, thus it's essential that indexes are
+      disabled ONLY for an empty table.
     */
     if (file->state->records == 0 && can_enable_indexes &&
         (!rows || rows >= MI_MIN_ROWS_TO_DISABLE_INDEXES))
@@ -1541,8 +1567,27 @@ int ha_myisam::end_bulk_insert()
 {
   mi_end_bulk_insert(file);
   int err=mi_extra(file, HA_EXTRA_NO_CACHE, 0);
-  return err ? err : can_enable_indexes ?
-                     enable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE) : 0;
+  if (!err)
+  {
+    if (can_enable_indexes)
+    {
+      /* 
+        Truncate the table when enable index operation is killed. 
+        After truncating the table we don't need to enable the 
+        indexes, because the last repair operation is aborted after 
+        setting the indexes as active and  trying to recreate them. 
+     */
+   
+      if (((err= enable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE)) != 0) && 
+                                                  current_thd->killed)
+      {
+        delete_all_rows();
+        /* not crashed, despite being killed during repair */
+        file->s->state.changed&= ~(STATE_CRASHED|STATE_CRASHED_ON_REPAIR);
+      }
+    } 
+  }
+  return err;
 }