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C.2.3 Changes in MySQL 5.2.3 (15 February 2007) »
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C.2.2. Changes in MySQL 5.2.4 (Not released)

This is a new Alpha development release, fixing recently discovered bugs.

Note

This Alpha release, as any other pre-production release, should not be installed on production level systems or systems with critical data. It is good practice to back up your data before installing any new version of software. Although MySQL has worked very hard to ensure a high level of quality, protect your data by making a backup as you would for any software beta release. Please refer to our bug database at http://bugs.mysql.com/ for more details about the individual bugs fixed in this version.

This section documents all changes and bug fixes that have been applied since the last official MySQL release. If you would like to receive more fine-grained and personalized update alerts about fixes that are relevant to the version and features you use, please consider subscribing to MySQL Network (a commercial MySQL offering). For more details please see http://www.mysql.com/products/enterprise/advisors.html.

Functionality added or changed:

  • Incompatible Change: Added the optimizer_use_mrr system variable to enable control over whether Multi Read Range optimization is used. This replaces the multi_range_count system variable, which has been removed.

  • The syntax for the LOCK TABLES statement has been extended to support transactional table locks that do not commit transactions automatically. Following LOCK TABLES ... IN SHARE MODE or LOCK TABLES ... IN EXCLUSIVE MODE, you can access tables not mentioned in the LOCK TABLES statement. You can now also issue these extended LOCK TABLES statements many times in succession, adding additional tables to the locked set, and without unlocking any tables that were locked previously. When using LOCK TABLES with IN SHARE MODE or IN EXCLUSIVE MODE, tables are not unlocked until the transaction is committed.

    The behavior of LOCK TABLES when not using IN SHARE MODE or IN EXCLUSIVE MODE remains unchanged.

  • A new SQL function, WEIGHT_STRING(), returns the weight string for an input string. The weight string represents the sorting and comparison value of the input string.

  • Added the optimizer_switch system variable to enable control over individual optimizations.

  • The maximum length of table comments was extended from 60 to 2048 characters. The maximum length of column comments was extended from 255 to 1024 characters. Index definitions now can include a comment of up to 1024 characters.

  • Parser performance was improved for identifier scanning and conversion of ASCII string literals.