Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment

CHECK TABLE did temporarily clear the auto_increment value.
It runs with a read lock, allowing other readers and
conurrent INSERTs. The latter could grab the wrong value
in this moment.

CHECK TABLE does no longer modify the auto_increment value.
Not even for a short moment.


myisam/mi_check.c:
  Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment
  In chk_key() and update_auto_increment_key() in the repair_only
  case, do not touch info->s->state.auto_increment. Especially
  chk_key() can be called from CHECK TABLE with a read lock.
  Concurrent inserts could grab a temporarily changed value.
  Added minor style fixes.
myisam/mi_key.c:
  Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment
  Changed update_auto_increment() to retrieve_auto_increment()
  to reflect that it does not change the auto_increment by
  itself any more. This must now be done externally if needed.
myisam/mi_update.c:
  Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment
  Added explicit update of info->s->state.auto_increment
  after the change from update_auto_increment() to
  retrieve_auto_increment().
myisam/mi_write.c:
  Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment
  Added explicit update of info->s->state.auto_increment
  after the change from update_auto_increment() to
  retrieve_auto_increment().
myisam/myisamdef.h:
  Bug#19604 - CHECK TABLE with concurrent INSERT can reset auto_increment
  Changed update_auto_increment() to retrieve_auto_increment()
  to reflect that it does not change the auto_increment by
  itself any more. This must now be done externally if needed.

1 files changed, 2 insertions, 1 deletions

diff --git a/myisam/mi_update.c b/myisam/mi_update.c
index 937c9983b45..f8b5cf55406 100644
--- a/myisam/mi_update.c
+++ b/myisam/mi_update.c
@@ -164,7 +164,8 @@ int mi_update(register MI_INFO *info, const byte *oldrec, byte *newrec)
       key_changed|= HA_STATE_CHANGED;		/* Must update index file */
   }
   if (auto_key_changed)
-    update_auto_increment(info,newrec);
+    set_if_bigger(info->s->state.auto_increment,
+                  retrieve_auto_increment(info, newrec));
   if (share->calc_checksum)
     info->state->checksum+=(info->checksum - old_checksum);