MDEV-15158 On commit, do not write to the TRX_SYS page
This is based on a prototype by Thirunarayanan Balathandayuthapani <thiru@mariadb.com>. Binlog and Galera write-set replication information was written into TRX_SYS page on each commit. Instead of writing to the TRX_SYS during normal operation, InnoDB can make use of rollback segment header pages, which are already being written to during a commit. The following list of fields in rollback segment header page are added: TRX_RSEG_BINLOG_OFFSET TRX_RSEG_BINLOG_NAME (NUL-terminated; empty name = not present) TRX_RSEG_WSREP_XID_FORMAT (0=not present; 1=present) TRX_RSEG_WSREP_XID_GTRID TRX_RSEG_WSREP_XID_BQUAL TRX_RSEG_WSREP_XID_DATA trx_sys_t: Introduce the fields recovered_binlog_filename, recovered_binlog_offset, recovered_wsrep_xid. To facilitate upgrade from older mysql or mariaDB versions, we will read the information in TRX_SYS page. It will be overridden by the information that we find in rollback segment header pages. Mariabackup --prepare will read the metadata from the rollback segment header pages via trx_rseg_array_init(). It will still not read any undo log pages or recover any transactions.
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