This is part of the ongoing work on improving the transaction life cycle management. In 5.7.2 we split the transaction list into two. The read-only transaction list and the read-write transaction list. There was another “virtual” list, the auto-commit non-locking read-only (AC-NL-RO) transaction list. The change in 5.7.2 was that by default a transaction was treated as read only and added to the read-only transaction list. Only when it was determined that the transaction was going to do an update we removed the transaction from the read-only list and moved it to the read-write transaction list. This initial add to the the read-only list forced the acquisition of the trx_sys_t::mutex. Acquiring the mutex during transaction start/begin has a cost. Promoting a transaction from read-only to read-write we had to acquire the trx_sys_t::mutex to add to the read-write transaction list and so that is not too expensive and is unavoidable. There is another …
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Jan
09
2014
Showing entries 1 to 1