• Marko Mäkelä's avatar
    MDEV-13534 InnoDB STATS_PERSISTENT fails to ignore garbage delete-mark flag on node pointer pages · e7bf8bca
    Marko Mäkelä authored
    This bug was a regression caused by MDEV-12698.
    
    On non-leaf pages, the delete-mark flag in the node pointer records is
    basically garbage. (Delete-marking only makes sense at the leaf level
    anyway. The purpose of the delete-mark is to tell MVCC, locking and purge
    that a leaf-level record does not exist in the READ UNCOMMITTED view,
    but it used to exist.)
    Node pointer records and non-leaf pages are glue that attaches multiple
    leaf pages to an index. This glue is supposed to be transparent to the
    transactional layer.
    
    When a page is split, InnoDB creates a node pointer record out of the
    child page record that the cursor is positioned on. The node pointer record
    for the parent page will be a copy of the child page record, amended with
    the child page number. If the child page record happened to carry the
    delete-mark flag, then the node pointer record would also carry this flag
    (even though the flag makes no sense outside child pages).
    
    (On a related note, for the first node pointer record in the first
    node pointer page of each tree level, if the MIN_REC_FLAG is set,
    the rest of the record contents (except the child page number)
    is basically garbage. From this garbage you could deduce at which point
    the child was originally split.)
    
    page_scan_method_t: Replace with bool, as there are only 2 values.
    
    dict_stats_scan_page(): Replace the parameter scan_method with is_leaf.
    Ignore the bogus (garbage) delete-mark flag if !is_leaf.
    e7bf8bca
innodb_stats_persistent_debug.result 652 Bytes