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Displaying posts with tag: trx_list scan (reset)
trx descriptors: MySQL performance improvements in Percona Server 5.5.30-30.2

One major problem in terms of MySQL performance that still stands in the way of InnoDB scalability is the trx_list scan on consistent read view creation. It was originally reported as a part of MySQL bug #49169 and can be described as follows. Whenever a connection wants to create a consistent read, it has to make a snapshot of the transaction states to determine which transactions are seen in the view later. To this end, InnoDB scans trx_list (i.e. the list of currently open transactions) and copies IDs of transactions that have not yet been committed at the current point in time, and thus should not be visible in the consistent read. For the REPEATABLE_READ isolation level, the snapshot is created on the first SELECT

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