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InnoDB auto-inc scalability fixed

 | September 26, 2007 |  Posted In: Insight for DBAs


There was long played scalability issue with InnoDB auto-increment field. For details check Bug 16979. In short words the problem is in case of insert into table with auto-increment column the special AUTO_INC table level lock is obtained, instead of usual row-level locks. With many concurrent inserted threads this causes serious scalability problems, and in our consulting practice we had a lot of customers who was affected by InnoDB auto-inc. For several of them we even advised to replace auto-inc column by that or another solution.
Good news is the bug is fixed. Bad news is it is fixed only 5.1.22, which is not released yet.
I wonder if the fix is going to be ported to 5.0, as I mentioned it affected many production systems and not all of them are ready to upgrade to 5.1.
The interesting also is the fix introduces new system variable innodb_autoinc_lock_mode which determines behavior of InnoDB for tables with autoinc. I do not want to copy-paste MySQL documentation, the very good and informative description of the problem and solution is available here.

Vadim Tkachenko

Vadim Tkachenko co-founded Percona in 2006 and serves as its Chief Technology Officer. Vadim leads Percona Labs, which focuses on technology research and performance evaluations of Percona’s and third-party products. Percona Labs designs no-gimmick tests of hardware, filesystems, storage engines, and databases that surpass the standard performance and functionality scenario benchmarks. Vadim’s expertise in LAMP performance and multi-threaded programming help optimize MySQL and InnoDB internals to take full advantage of modern hardware. Oracle Corporation and its predecessors have incorporated Vadim’s source code patches into the mainstream MySQL and InnoDB products. He also co-authored the book High Performance MySQL: Optimization, Backups, and Replication 3rd Edition.


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