WL#3071 - Maria checkpoint

don't take a checkpoint at end of REDO phase because blocks' rec_lsn
are not set. Fixes some assertion failures during tests of killing
the UNDO phase (recovery then started from the end-of-REDO-phase
checkpoint, wrongly ignoring REDOs before that record).


storage/maria/ma_blockrec.c:
  note for a bug (mail sent to colleagues, put on todo)
storage/maria/ma_recovery.c:
  this checkpoint at end of REDO phase is incorrect, disabling it.
  The one at end of UNDO phase remains.

storage/maria/ma_blockrec.c

@@ -1537,6 +1537,7 @@ static my_bool write_full_pages(MARIA_HA *info,
     length-= copy_length;
 
     DBUG_ASSERT(share->pagecache->block_size == block_size);
+    /** @todo RECOVERY BUG the page does not get a rec_lsn with this! */
     if (pagecache_write(share->pagecache,
                         &info->dfile, page, 0,
                         buff, share->page_type,

storage/maria/ma_recovery.c

@@ -298,6 +298,15 @@ int maria_apply_log(LSN from_lsn, enum maria_apply_log_way apply,
     fprintf(stderr, " (%.1f seconds); ", phase_took);
   }
 
+  /**
+     REDO phase does not fill blocks' rec_lsn, so a checkpoint now would be
+     wrong: if a future recovery used it, the REDO phase would always
+     start from the checkpoint and never from before, wrongly skipping REDOs
+     (tested).
+
+     @todo fix this.
+  */
+#if 0
   if (take_checkpoints && checkpoint_useful)
   {
     /*
@@ -308,6 +317,7 @@ int maria_apply_log(LSN from_lsn, enum maria_apply_log_way apply,
     if (ma_checkpoint_execute(CHECKPOINT_INDIRECT, FALSE))
       goto err;
   }
+#endif
 
   if (should_run_undo_phase)
   {