The limit of 255 characters on the input buffer for mysql on Windows has been lifted. The exact limit depends on what the system allows, but can be up to 64K characters. A typical limit is 16K characters. (Bug#12929)

Added the myisam_stats_method, which controls whether NULL values in indexes are considered the same or different when collecting statistics for MyISAM tables. This influences the query optimizer as described in Section 7.4.7, “MyISAM Index Statistics Collection”. (Bug#12232)

• Better detection of connection timeout for replication servers on Windows allows elimination of extraneous Lost connection errors in the error log. (Bug#5588)

• When using IF NOT EXISTS with CREATE DATABASE or CREATE TABLE, a warning now is generated if the database or table already exists. (Bug#6008):

• A new command line argument was added to mysqld to ignore client character set information sent during handshake, and use server side settings instead, to reproduce 4.0 behavior (Bug#9948):

  mysqld --skip-character-set-client-handshake

• A prepared statement failed with Illegal mix of collations if the client character set was utf8 and the statement used a table that had a character set of latin1. (Bug#12371)

• If special characters such as '_' , '%', or the escape character were included within the prefix of a column index, LIKE pattern matching on the indexed column did not return the correct result. (Bug#13046, Bug#13919)

• NDBCluster: Updating a text-type column during a cluster backup could cause the ndbd process to crash, due to the incorrect use of charset-normalized reads for. This could also lead to “wrong” data in the backup if such a column was updated during the backup; for example, supposing that the column used latin_ci, then “aAa” might be stored in the backup as “AAA”. (Bug#12950)

• NDBCluster: When performing a delete of a great many (tens of thousands of) rows at once from a Cluster table, an improperly dereferenced pointer could cause the mysqld process to crash. (Bug#9282)

• Server could over-allocate memory when performing a FULLTEXT search for stopwords only. (Bug#13582)

• UNION of two DECIMAL columns returned wrong field type. (Bug#13372)

• CHECKSUM TABLE locked InnoDB tables and did not use a consistent read. (Bug#12669)

• SHOW CREATE TABLE did not display any FOREIGN KEY clauses if a temporary file could not be created. Now SHOW CREATE TABLE displays an error message in an SQL comment if this occurs. (Bug#13002)

• Display of the AUTO_INCREMENT attribute by SHOW CREATE TABLE was not controlled by the NO_FIELD_OPTIONS SQL mode as it should have been. (Bug#7977)

• For VARCHAR columns with the ucs2 character set, InnoDB trimmed trailing 0x20 bytes rather than 0x0020 words, resulting in incorrect index lookups later. (Bug#12178)

• MySQL programs in binary distributions for Solaris 8/9/10 x86 systems would not run on Pentium III machines. (Bug#6772)

• NDB Cluster: Multiple ndb_mgmd processes in a cluster would not know each other's IP addresses. (Bug#12037)

• NDB Cluster: With two mgmd processes in a cluster, ndb_mgm output for SHOW would display the same IP address for both processes, even when they were on different hosts. (Bug#11595)

• The --replicate-rewrite-db and --replicate-do-table options did not work for statements in which tables were aliased to names other than those listed by the options. (Bug#11139)

• After running configure with the --with-embedded-privilege-control option, the embedded server failed to build. (Bug#13501)

• Queries against a MERGE table that has a composite index could produce incorrect results. (Bug#9112)

• Comparisons involving row constructors containing constants could cause a server crash. (Bug#13356)

• MySQL would pass an incorrect key length to storage engines for MIN(). This could cause warnings such as InnoDB: Warning: using a partial-field key prefix in search. in the .err log. (Bug#13218, same as Bug#11039 in MySQL 5.0.7)

• NDB Cluster: LOAD DATA INFILE with a large data file failed. (Bug#10694)

• NDB Cluster: Adding an index to a table with a large number of columns (more then 100) crashed the storage node. (Bug#13316)

• Aggregate functions sometimes incorrectly were allowed in the WHERE clause of UPDATE and DELETE statements. (Bug#13180)

• MIN() and MAX() sometimes returned a non-NULL value for an empty row set (for example, SELECT MAX(1) FROM empty_table). (Bug#12882)

• LOAD DATA INFILE did not respect the NO_AUTO_VALUE_ON_ZERO SQL mode setting. (Bug#12053)

• Use of a user-defined function within the HAVING clause of a query resulted in an Unknown column error. (Bug#11553)

• The data type for DECIMAL columns was not respected when updating the column from another column. For example, updating a DECIMAL(10,1) column with the value from a DECIMAL(10,5) column resulted in a DECIMAL(10,5) value being stored. Similarly, altering a column with a DECIMAL(10,5) datatype to a DECIMAL(10,1) data type did not properly convert data values. (Bug#7598)

• NDB: A cluster shutdown following the crash of a data node would fail to terminate the remaining node processes, even though ndb_mgm showed the shutdown request as having been completed. (Bug#10938, Bug#9996, Bug#11623)

• For queries with DISTINCT and WITH ROLLUP, the DISTINCT should be applied after the rollup operation, but was not always. (Bug#12887)

• The counters for the Key_read_requests, Key_reads, Key_write_requests, and Key_writes status variables were changed from unsigned long to unsigned longlong to accommodate larger values before the variables roll over and restart from 0. (Bug#12920)

• A column that can be NULL was not handled properly for WITH ROLLUP in a subquery or view. (Bug#12885)

• Shared-memory connections were not working on Windows. (Bug#12723)

• A concurrency problem for CREATE ... SELECT could cause a server crash. (Bug#12845)

• Performing an IS NULL check on the MIN() or MAX() of an indexed column in a complex query could produce incorrect results. (Bug#12695)

• The NDB START BACKUP command could be interrupted by a SHOW command. (Bug#13054)

• The LIKE ... ESCAPE syntax produced invalid results when escape character was larger than one byte. (Bug#12611)

• A client connection thread cleanup problem caused the server to crash when closing the connection if the binary log was enabled. (Bug#12517)

• CHECKSUM TABLE command returned incorrect results for tables with deleted rows. After upgrading, users who used stored checksum information to detect table changes should rebuild their checksum data. (Bug#12296)

• The value of character_set_results could be set to NULL, but returned the string "NULL" when retrieved. (Bug#12363)

• GROUP_CONCAT() ignored an empty string if it was the first value to occur in the result. (Bug#12863)

• Outer join elimination was erroneously applied for some queries that used a NOT BETWEEN condition, an IN(value_list) condition, or an IF() condition. (Bug#12101, Bug#12102)

• Reverted a change introduced in MySQL 4.1.13 to fix a problem of SHOW FIELDS truncating the TYPE column to 40 characters. This fix was reverted for MySQL 4.1 because it broke existing applications. The fix will be made to MySQL 5.0 instead (5.0.13). (Bug#7142, Bug#12817)

• On HP-UX 11.x (PA-RISC), the -L option caused mysqlimport to crash. (Bug#12958)

• After changing the character set with SET CHARACTER SET, the result of the GROUP_CONCAT() function was not converted to the proper character set. (Bug#12829)

• myisampack did not properly pack BLOB values larger than 2²⁴ bytes. (Bug#4214)

• The server crashed when one thread resized the query cache while another thread was using it. (Bug#12848)

• mysqld_multi now quotes arguments on command lines that it constructs to avoid problems with arguments that contain shell metacharacters. (Bug#11280)

• When any --replicate-wild-* option is used, the slave ignores SET ONE_SHOT TIME_ZONE statements as belonging to a non-replicated table. (Bug#12542)

• Deadlock occurred when several account management statements were run (particularly between FLUSH PRIVILEGES/SET PASSWORD and GRANT/REVOKE statements). (Bug#12423)

• On Windows, the server was preventing tables from being created if the table name was a prefix of a forbidden name. For example, nul is a forbidden name because it's the same as a Windows device name, but a table with the name of n or nu was being forbidden as well. (Bug#12325)

• InnoDB was too permissive with LOCK TABLE ... READ LOCAL and allowed new inserts into the table. Now READ LOCAL is equivalent to READ for InnoDB. This will cause slightly more locking in mysqldump, but makes InnoDB table dumps consistent with MyISAM table dumps. (Bug#12410)

• The have_innodb read-only system variable could not be selected with SELECT @@have_innodb. (Bug#9613)

• A UNION of long utf8 VARCHAR columns was sometimes returned as a column with a LONGTEXT data type rather than VARCHAR. This could prevent such queries from working at all if selected into a MEMORY table because the MEMORY storage engine does not support the TEXT data types. (Bug#12537)

• NDB Cluster: Corrected the parsing of the CLUSTERLOG command by ndb_mgm to allow multiple items. (Bug#12833)

• NDB Cluster: Improved error messages related to filesystem issues. (Bug#11218)

• NDB Cluster: When a schema was detected to be corrupt, ndb neglected to close it, resulting in a “file already open” error if the schema was opened again later. written. (Bug#12027)

• NDB Cluster: When it could not copy a fragment, ndbd exited without printing a message about the condition to the error log. Now the message is written. (Bug#12900)

• NDB Cluster: When a disk full condition occurred, ndbd exited without printing a message about the condition to the error log. Now the message is written. (Bug#12716)

• If a client has opened an InnoDB table for which the .ibd file is missing, InnoDB would not honor a DROP TABLE statement for the table. (Bug#12852)

• SELECT GROUP_CONCAT(...) FROM DUAL in a subquery could cause the client to hang. (Bug#12861)

• NDB Cluster: Bad values in config.ini caused ndb_mdmd to crash. (Bug#12043)

• TRUNCATE TABLE did not work with TEMPORARY InnoDB tables. (Bug#11816)

• ALTER TABLE db_name.t RENAME t did not move the table to default database unless the new name was qualified with the database name. (Bug#11493)

• Spatial index corruption could occur during updates. (Bug#9645)

• If a DROP DATABASE fails on a master server due to the presence of a non-database file in the database directory, the master have the database tables deleted, but not the slaves. To deal with failed database drops, we now write DROP TABLE statements to the binary log for the tables so that they are dropped on slaves. (Bug#4680)

• DELETE or UPDATE for an indexed MyISAM table could fail. This was due to a change in end-space comparison behavior from 4.0 to 4.1. (Bug#12565)

• The ARCHIVE storage engine does not support deletes, but it was possible to delete by using DELETE or TRUNCATE TABLE with a FEDERATED table that points to an ARCHIVE table. (Bug#12836)

• Queries that created implicit temporary tables could return incorrect data types for some columns. (Bug#11718)

• An optimizer estimate of zero rows for a non-empty InnoDB table used in a left or right join could cause incomplete rollback for the table. (Bug#12779)

• A SELECT DISTINCT query with a constant value for one of the columns would return only a single row. (Bug#12625)

• Users created using an IP address or other alias rather than a hostname listed in /etc/hosts could not set their own passwords. (Bug#12302)

• NDB Cluster: An ALTER TABLE command caused loss of data stored prior to the issuing of the command. (Bug#12118)

• MEMORY tables using B-Tree index on 64-bit platforms could produce false table is full errors. (Bug#12460)

• MySQL failed to compile when --with-ndb-ccflags was specified. (Bug#11538)

• On Windows when the --innodb_buffer_pool_awe_mem_mb option has been given, the server detects whether AWE support is available and has been compiled into the server, and displays an appropriate error message if not. (Bug#6581)