Changes in MySQL 5.6.26 (2015-07-24, General Availability)

This release adds support for Debian 8 and Ubuntu 15.04.

• MySQL Enterprise Notes

• Performance Schema Notes

• Security Notes

• Functionality Added or Changed

• Bugs Fixed

MySQL Enterprise Notes

• MySQL Enterprise Edition incorporates these changes for MySQL Enterprise Firewall:

  • The firewall implements a DETECTING intrusion-detection mode. For accounts in this mode, the firewall detects suspicious statements and writes them to the error log but does not deny access. The new Firewall_access_suspicious status variable counts the number of such statements. The sp_set_firewall_mode() stored procedure now synchronizes between in-memory rules and those in persistent storage for DETECTING mode, just as it does for PROTECTING mode.

  • A new sp_reload_firewall_rules() stored procedure reloads the in-memory rules for a registered account from the rules stored in the mysql.firewall_whitelist table, providing better control over firewall operation for individual accounts.

  • A new mysql_firewall_flush_status() function resets firewall access-counter status variables.

  To upgrade MySQL Enterprise Firewall if you have a version installed from a previous release, first uninstall the old version. Then install the new version and register your firewall configuration again. For instructions, see Installing or Uninstalling MySQL Enterprise Firewall.

Performance Schema Notes

• Current-event timing now provides more information. Previously, while a wait, stage, or statement event was executing, the respective tables displayed the event with TIMER_START populated, but with TIMER_END and TIMER_WAIT as NULL:

  events_waits_current
  events_stages_current
  events_statements_current

  To make it possible to determine how long a not-yet-completed event has been running, the timer columns now are set as follows:

  • TIMER_START is populated (unchanged from previous behavior)

  • TIMER_END is populated with the current timer value

  • TIMER_WAIT is populated with the time elapsed so far (TIMER_END − TIMER_START)

  To find events that have not yet completed (that is, have no END_EVENT_ID) and have taken longer than N picoseconds thus far, monitoring applications can use this expression in queries:

  WHERE END_EVENT_ID IS NULL AND TIMER_WAIT > N

  (Bug #75156, Bug #20889406)

Security Notes

• Due to the LogJam issue (https://weakdh.org/), OpenSSL has changed the Diffie-Hellman key length parameters for openssl-1.0.1n and up. OpenSSL has provided a detailed explanation at http://openssl.org/news/secadv_20150611.txt. To adopt this change in MySQL, the following modifications were made:

  • The key length used in vio/viosslfactories.c for creating Diffie-Hellman keys has been increased from 512 to 2,048 bits.

  • The linked OpenSSL library for the MySQL Commercial Server has been updated from version 1.0.1m to version 1.0.1p. Issues fixed in the new version are described at http://www.openssl.org/news/vulnerabilities.html. This change does not affect the Oracle-produced MySQL Community build of MySQL Server, which uses the yaSSL library instead.

  (Bug #77275, Bug #21221862, Bug #18367167, Bug #21307471, Bug #21449838)

Functionality Added or Changed

• Replication: When using a multithreaded slave, each worker thread has its own queue of transactions to process. In previous MySQL versions, STOP SLAVE waited for all workers to process their entire queue. This logic has been changed so that STOP SLAVE first finds the newest transaction that was committed by any worker thread. Then, it waits for all workers to complete transactions older than that. Newer transactions are not processed. The new logic allows STOP SLAVE to complete faster in case some worker queues contain multiple transactions. (Bug #75525, Bug #20369401)

• Previously, the max_digest_length system variable controlled the maximum digest length for all server functions that computed statement digests. However, whereas the Performance Schema may need to maintain many digest values, other server functions such as MySQL Enterprise Firewall need only one digest per session. Increasing the max_digest_length value has little impact on total memory requirements for those functions, but can increase Performance Schema memory requirements significantly. To enable configuring digest length separately for the Performance Schema, its digest length is now controlled by the new performance_schema_max_digest_length system variable. (Bug #20963147)

• Previously, changes to the validate_password plugin dictionary file (named by the validate_password_dictionary_file system variable) while the server was running required a restart for the server to recognize the changes. Now validate_password_dictionary_file can be set at runtime and assigning a value causes the named file to be read without a restart.

  In addition, two new status variables are available. validate_password_dictionary_file_last_parsed indicates when the dictionary file was last read, and validate_password_dictionary_file_words_count indicates how many words it contains. (Bug #66697, Bug #14588145)

Bugs Fixed

• InnoDB: The ib_cursor_moveto function did not accept a search tuple with fewer fields than are defined for the index. (Bug #21121197, Bug #77083)

• InnoDB: The ib_table_truncate function failed to release a transaction, resulting in a hang on server shutdown. (Bug #21121164, Bug #77084)

• InnoDB: The ib_open_table_by_id function passed an incorrect argument to dict_table_open_on_id. (Bug #21121084, Bug #77100)

• InnoDB: On Unix-like platforms, os_file_create_simple_no_error_handling_func and os_file_create_func opened files in different modes when innodb_flush_method was set to O_DIRECT. (Bug #21113036, Bug #76627)

• InnoDB: Opening a foreign key-referenced table with foreign_key_checks enabled resulted in an error when the table or database name contained special characters. (Bug #21094069, Bug #77043)

• InnoDB: The page_zip_verify_checksum function returned false for a valid compressed page. (Bug #21086723)

• InnoDB: An ALTER TABLE ... IMPORT TABLESPACE operation on a table with prefix index failed with a schema mismatch error. (Bug #20977779, Bug #76877)

• InnoDB: A failure to load a change buffer bitmap page during a concurrent delete tablespace operation caused a server exit. (Bug #20878735)

• InnoDB: An assertion was raised when InnoDB attempted to dereference a NULL foreign key object. (Bug #20762798)

• InnoDB: Importing a tablespace with a full-text index resulted in an assertion when attempting to rebuild the index. (Bug #20637494)

• InnoDB: After dropping a full-text search index, the hidden FTS_DOC_ID and FTS_DOC_ID_INDEX columns prevented online DDL operations. (Bug #20590013, Bug #76012)

• InnoDB: The InnoDB memcached plugin handled unsigned NOT NULL integer columns incorrectly. Thanks to Piotr Jurkiewicz for the patch. (Bug #20535517, Bug #75864)

• InnoDB: A DROP DATABASE operation raised an assertion. (Bug #19929435)

• InnoDB: An index record was not found on rollback due to inconsistencies in the purge_node_t structure. The inconsistency resulted in warnings and error messages such as “error in sec index entry update”, “unable to purge a record”, and “tried to purge sec index entry not marked for deletion”. (Bug #19138298, Bug #70214, Bug #21126772, Bug #21065746)

• Partitioning: In certain cases, ALTER TABLE ... REBUILD PARTITION was not handled correctly when executed on a locked table. (Bug #75677, Bug #20437706)

• Replication: When using GTIDs, a multithreaded slave which had relay_log_recovery=1 and that stopped unexpectedly could encounter a relay-log-recovery cannot be executed when the slave was stopped with an error or killed in MTS mode error upon restart. The fix ensures that the relay log recovery process checks if GTIDs are in use or not. If GTIDs are in use, the multithreaded slave recovery process uses the GTID protocol to fill any unprocessed transactions. (Bug #73397, Bug #19316063)

• Replication: When two slaves with the same server_uuid were configured to replicate from a single master, the I/O thread of the slaves kept reconnecting and generating new relay log files without new content. In such a situation, the master now generates an error which is sent to the slave. By receiving this error from the master, the slave I/O thread does not try to reconnect, avoiding this problem. (Bug #72581, Bug #18731252)

• Incorrect cost calculation for the semijoin Duplicate Weedout strategy could result in a server exit. (Bug #21184091)

• MySQL Enterprise Firewall recorded prepared statements as they were received by the server, not as normalized digests. (Bug #20929568)

• For MySQL Enterprise Firewall operation, max_digest_length had to be larger than mysql_firewall_max_query_size or normalized statements were truncated. The mysql_firewall_max_query_size has been removed so that issue no longer applies, but max_digest_length should still be set large enough to avoid statement truncation. (Bug #20894024)

• Enabling MySQL Enterprise Firewall and binary logging could result in the server reading freed memory. (Bug #20848324)

• For large values of max_digest_length, the Performance Schema could encounter an overflow error when computing memory requirements, resulting in a server exit. (Bug #20738072)

• The Spencer regex library used for the REGEXP operator could be subject to heap overflow in some circumstances. (Bug #20642505)

• A buffer-overflow error could occur for mysqlslap during option parsing. (Bug #20605441)

• An off-by-one error in string-copying code could result in a buffer overflow. (Bug #20359808)

• GROUP BY or ORDER BY on a CHAR(0) NOT NULL column could lead to a server exit. (Bug #19660891)

• For some status variables that should monotonically increase, SHOW GLOBAL STATUS in one session could show them as decreasing when other concurrent sessions changed user or disconnected. (Bug #18591145)

• An unnecessary memset() call invoked during Performance Schema digest operations has been removed, which improves performance by reducing overhead. (Bug #77863, Bug #21528683)

• mysql-systemd-start failed if datadir was set in /etc/my.cnf. (Bug #77357, Bug #21262883)

• Compilation failed when building MySQL without the Performance Schema. (Bug #77292, Bug #21229433)

• A call to the MySQL Enterprise Firewall sp_set_firewall_mode() stored procedure with an invalid user name produced an error but added the user to the firewall_users table anyway. (Bug #76914, Bug #21021875)

• Identifiers in normalized statements were sometimes quoted and sometimes not, an inconsistency that caused matching failure for statement digests and digest texts. This caused problems for MySQL Enterprise Firewall and for Performance Schema aggregation by digest. Identifiers now are quoted consistently. (Bug #76723, Bug #20896539)

• Ubuntu packages were missing dependencies for killall and psmisc. (Bug #76716, Bug #20893836)

• On OS X 10.10 (Yosemite), mysqld failed to start automatically. The startup item has been replaced with a launchd job, which enables the preference pane check box for automatic startup to work again. (Bug #74434, Bug #19858350)

• When choosing join order, the optimizer could incorrectly calculate the cost of a table scan and choose a table scan over a more efficient eq_ref join. (Bug #71584, Bug #18194196)