mysqltest now installs signal handlers and generates a stack trace if it crashes. (Bug#37003)

mysqltest was changed to be more robust in the case of a race condition that can occur for rapid disconnect/connect sequences with the server. The account used by mysqltest could reach its allowed simultaneous-sessions user limit if the connect attempt occurred before the server had fully processed the preceding disconnect. mysqltest now checks specificaly for a user-limits error when it connects; if that error occurs, it delays briefly before retrying. (Bug#23921)

Improvements made to MySQL Backup (the BACKUP DATABASE and RESTORE statements):

Security Enhancement: The server consumed excess memory while parsing statements with hundreds or thousands of nested boolean conditions (such as OR (OR ... (OR ... ))). This could lead to a server crash or incorrect statement execution, or cause other client statements to fail due to lack of memory. The latter result constitutes a denial of service. (Bug#38296)

Partitioning: A LIST partitioned MyISAM table returned erroneous results when an index was present on a column in the WHERE clause and NOT IN was used on that column.

Searches using the index were also much slower then if the index were not present. (Bug#35931)

Partitioning: SELECT COUNT(*) was not correct for some partitioned tables using a storage engine that did not support HA_STATS_RECORDS_IS_EXACT. Tables using the ARCHIVE storage engine were known to be affected.

This was because ha_partition::records() was not implemented, and so the default handler::records() was used in its place. However, this is not correct behavior if the storage engine does not support HA_STATS_RECORDS_IS_EXACT.

The solution was to implement ha_partition::records() as a wrapper around the underlying partition records.

As a result of this fix, the rows column in the output of EXPLAIN PARTITIONS now includes the total number of records in the partitioned table. (Bug#35745)

Replication: When AUTOCOMMIT was set equal to 1 after starting a transaction, the binary log did not commit the outstanding transaction. The reason this happened was that the binary log commit function saw only the values of the new settings, and decided that there was nothing to commit.

This issue was first observed when using the Falcon storage engine, but it is possible that it affected other storage engines as well. (Bug#37221)

Replication: Some kinds of internal errors (such as Out of stack) cuased the server to crash. (Bug#37150)

Replication: Row-based replication did not correctly copy TIMESTAMP values from a big-endian storage engine to a little-endian storage engine. (Bug#37076)

Replication: Performing an insert on a table having an AUTO_INCREMENT column and an INSERT trigger that was being replicated from a master running MySQL 5.0 or any version of MySQL 5.1 up to and including MySQL 5.1.11 to a slave running MySQL 5.1.12 or later caused the replication slave to crash. (Bug#36443)

See also Bug#33029

Server-side cursors were not initialized properly, which could cause a server crash. (Bug#38486)

The fix for Bug#20748 caused a problem such that on Unix, MySQL programs looked for options in ~/my.cnf rather than the standard location of ~/.my.cnf. (Bug#38180)

MyISAM tables with non-ASCII characters in their names could not be backed up because the MyISAM native backup driver did not handle them properly. (Bug#38045)

If the table definition cache contained tables with many BLOB columns, much memory could be allocated to caching BLOB values. Now a size limit on the cached BLOB values is enforced. (Bug#38002)

For InnoDB tables, ORDER BY ... DESC sometimes returned results in ascending order. (Bug#37830)

The server returned unexpected results if a right side of the NOT IN clause consisted of the NULL value and some constants of the same type. For example, this query might return 3, 4, 5, and so forth if a table contained those values:

SELECT * FROM t WHERE NOT t.id IN (NULL, 1, 2);

(Bug#37761)

Setting the session value of the innodb_table_locks system variable caused a server crash. (Bug#37669)

Nesting of IF() inside of SUM() could cause an extreme server slowdown. (Bug#37662)

For BACKUP DATABASE, if the WITH COMPRESSION clause was not used, an uninitialized variable could cause unpredictable results. (Bug#37654)

Killing a query that used an EXISTS subquery as the argument to SUM() or AVG() caused a server crash. (Bug#37627)

NOT IN subqueries that selected MIN() or MAX() values but produced an empty result could cause a server crash. (Bug#37004)

SELECT DISTINCT from a simple view on an InnoDB table, where all selected columns belong to the same unique index key, returned incorrect results. (Bug#36632)

RESTORE could fail if the server on which the restore operation took place had enabled triggers or events. (Bug#36530)

CHAR(256 USING utf32) could generate a result with an incorrect length and result in a server crash. (Bug#36418)

The UUID() function returned UUIDs with the wrong time; this was because the offset for the time part in UUIDs was miscalculated. (Bug#35848)

The configure script did not allow utf8_hungarian_ci to be specified as the default collation. (Bug#35808)

Freeing of an internal parser stack during parsing of complex stored programs caused a server crash. (Bug#35577, Bug#37269, Bug#37728)

The code for detecting a byte order mark (BOM) caused mysql to crash for empty input. (Bug#35480)

Index scans performed with the sort_union() access method returned bad data when the sort_buffer_size limit was reached. (Bug#35478)

BACKUP DATABASE caused a server crash if it attempted to back up a view that depended on another view. (Bug#34758, Bug#35347)

A significant slowdown occurred when many SELECT statements that return many rows from InnoDB tables were running concurrently. (Bug#34409)

mysql_install_db failed if the server was running with a SQL mode of TRADITIONAL. This program now resets the SQL mode internally to avoid this problem. (Bug#34159)

Fast ALTER TABLE operations were not fast for columns that used multibyte character sets. (Bug#33873)

ORDER BY failed to take into account accents and lettercases in multi-level collations (latin2_czech_cs and cp1250_czech_cs). (Bug#33791, Bug#30462)

The internal functions my_getsystime(), my_micro_time(), and my_micro_time_and_time() did not work correctly on Windows. One symptom was that uniqueness of UUID() values could be compromised. (Bug#33748)

The SHOW FUNCTION CODE and SHOW PROCEDURE CODE statements are not present in non-debug builds, but attempting to use them resulted in a “syntax error” message. Now the error message indicates that the statements are disabled and that you must use a debug build. (Bug#33637)

If a large number of databases were named in the BACKUP DATABASE statement, the server crashed. (Bug#33568)

Cached queries that used 256 or more tables were not properly cached, so that later query invalidation due to a TRUNCATE TABLE for one of the tables caused the server to hang. (Bug#33362)

BACKUP DATABASE did not properly set the flags in the first two bytes of the backup image. (Bug#33120)

Unindexed ORDER BY did not work on short utf32 columns, or on utf16 columns with a short max_sort_length value. (Bug#33073)

After an upgrade to MySQL 6.0.4 or higher, columns that used the old 3-byte Unicode utf8 character set are treated as having the utf8mb3 character set. mysql_upgrade did not convert all system tables in the mysql database to use the new 4-byte Unicode utf8 character set rather than utf8mb3. This caused problems such as that the event scheduler would not start. mysql_upgrade now performs the utf8mb3 to utf8 conversion for system tables. (Bug#33002, Bug#33053)

It was possible to insert invalid Unicode characters (with code point values greater than U+10FFFF) into utf8 and utf32 columns. (Bug#32914)

Inserting CURRENT_TIME, CURRENT_DATE, or CURRENT_TIMESTAMP into a VARCHAR column didn't work for non-ASCII character sets such as ucs2, utf16, or utf32. (Bug#32390)

mysql_upgrade attempted to use the /proc filesystem even on systems that do not have it. (Bug#31605)

Making INFORMATION_SCHEMA the default database caused the DROP TABLESPACE statement to be disabled. (Bug#31302)

The Serbian translation for the ER_INCORRECT_GLOBAL_LOCAL_VAR error was corrected. (Bug#29738)

The XPath boolean() function did not cast string and nodeset values correctly in some cases. It now returns TRUE for any non-empty string or nodeset and 0 for a NULL string, as specified in the XPath standard.. (Bug#26051)

The FLUSH PRIVILEGES statement did not produce an error when it failed. (Bug#21226)

After executing a prepared statement that accesses a stored function, the next execution would fail to find the function if the stored function cache was flushed in the meantime. (Bug#12093, Bug#21294)

perror did not work for errors described in the sql/share/errmsg.txt file. (Bug#10143)