• Marko Mäkelä's avatar
    MDEV-28601 InnoDB history list length was reverted to 32 bits · 99c8aed0
    Marko Mäkelä authored
    srv_do_purge(): In commit edde1f6e
    when the de-facto 32-bit trx_sys_t::history_size() was replaced with
    32-bit trx_sys.rseg_history_len, some more variables were changed
    from ulint (size_t) to uint32_t.
    
    The history list length is the number of committed transactions whose
    undo logs are waiting to be purged. Each TRX_RSEG_HISTORY list is
    storing the number of entries in a 32-bit field and each transaction
    will occupy at least one undo log page. It is thinkable that the
    length of each TRX_RSEG_HISTORY list may approach the maximum
    representable number. The number cannot be exceeded, because the
    rollback segment header is allocated from the same tablespace as
    the undo log header pages it is pointing to, and because the page
    numbers of a tablespace are stored in 32 bits. In any case, it is
    possible that the total number of unpurged committed transactions
    cannot be represented in 32 but 39 bits (corresponding to
    128 rollback segments and undo tablespaces).
    99c8aed0
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