Incompatible change: Previously, the DATE_FORMAT() function returned a binary string. Now it returns a string with a character set and collation given by character_set_connection and collation_connection so that it can return month and weekday names containing non-ASCII characters. (Bug#22646)

Incompatible change: The prepared_stmt_count system variable has been converted to the Prepared_stmt_count global status variable (viewable with the SHOW GLOBAL STATUS statement). (Bug#23159)

mysqldump --single-transaction now uses START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT */ rather than BEGIN to start a transaction, so that a consistent snapshot will be used on those servers that support it. (Bug#19660)

Important: When using MERGE tables the definition of the MERGE table and the MyISAM tables are checked each time the tables are opened for access (including any SELECT or INSERT statement. Each table is compared for column order, types, sizes and associated. If there is a difference in any one of the tables then the statement will fail.

The --memlock option relies on system calls that are unreliable on some operating systems. If a crash occurs, the server now checks whether --memlock was specified and if so issues some information about possible workarounds. (Bug#22860)

The server now includes a timestamp in error messages that are logged as a result of unhandled signals (such as mysqld got signal 11 messages). (Bug#24878)

Incompatible change: For ENUM columns that had enumeration values containing commas, the commas were mapped to 0xff internally. However, this rendered the commas indistinguishable from true 0xff characters in the values. This no longer occurs. However, the fix requires that you dump and reload any tables that have ENUM columns containing true 0xff in their values: Dump the tables using mysqldump with the current server before upgrading from a version of MySQL 4.1 older than 4.1.23 to version 4.1.23 or newer. (Bug#24660)

Incompatible change: INSERT DELAYED statements are not supported for MERGE tables, but the MERGE storage engine was not rejecting such statements, resulting in table corruption. Applications previously using INSERT DELAYED into MERGE table will break when upgrading to versions with this fix. To avoid the problem, remove DELAYED from such statements. (Bug#26464)

For MERGE tables defined on underlying tables that contained a short VARCHAR column (shorter than four characters), using ALTER TABLE on at least one but not all of the underlying tables caused the table definitions to be considered different from that of the MERGE table, even if the ALTER TABLE did not change the definition. Also, when the underlying tables contained a TINYINT or CHAR(1) column, the MERGE storage engine incorrectly reported that they differed from the MERGE table in certain cases. (Bug#26881)

Incorrect results could be returned for some queries that contained a select list expression with IN or BETWEEN together with an ORDER BY or GROUP BY on the same expression using NOT IN or NOT BETWEEN. (Bug#27532)

GRANT statements were not replicated if the server was started with the --replicate-ignore-table or --replicate-wild-ignore-table option. (Bug#25482)

For MyISAM tables, COUNT(*) could return an incorrect value if the WHERE clause compared an indexed TEXT column to the empty string (''). This happened if the column contained empty strings and also strings starting with control characters such as tab or newline. (Bug#26231)

Duplicate entries were not assessed correctly in a MEMORY table with a BTREE primary key on a utf8 ENUM column. (Bug#24985)

Storing NULL values in spatial fields caused excessive memory allocation and crashes on some systems. (Bug#27164)

In a MEMORY table, using a BTREE index to scan for updatable rows could lead to an infinite loop. (Bug#26996)

The range optimizer could cause the server to run out of memory. (Bug#26625)

Difficult repair or optimization operations could cause an assertion failure, resulting in a server crash. (Bug#25289)

DOUBLE values such as 20070202191048.000000 were being treated as illegal arguments by WEEK(). (Bug#23616)

If a thread previously serviced a connection that was killed, excessive memory and CPU use by the thread occurred if it later serviced a connection that had to wait for a table lock. (Bug#25966)

LOAD DATA INFILE sent an okay to the client before writing the binary log and committing the changes to the table had finished, thus violating ACID requirements. (Bug#26050)

In certain cases it could happen that deleting a row corrupted an RTREE index. This affected indexes on spatial columns. (Bug#25673)

Added support for --debugger=dbx for mysql-test-run.pl and fixed support for --debugger=devenv, --debugger=DevEnv, and --debugger=/path/to/devenv. (Bug#26792)

X() IS NULL and Y() IS NULL comparisons failed when X() and Y() returned NULL. (Bug#26038)

UNHEX() IS NULL comparisons failed when UNHEX() returned NULL. (Bug#26537)

A reference to a non-existent column in the ORDER BY clause of an UPDATE ... ORDER BY statement could cause a server crash. (Bug#25126)

The creation of MySQL system tables was not checked for by mysql-test-run.pl. (Bug#20166)

NOW() returned the wrong value in statements executed at server startup with the --init-file option. (Bug#23240)

For ALTER TABLE, using ORDER BY expression could cause a server crash. Now the ORDER BY clause allows only column names to be specified as sort criteria (which was the only documented syntax, anyway). (Bug#24562)

Storing values specified as hexadecimal values 64 or more bits long into BIGINT or BIGINT UNSIGNED columns did not raise any warning or error if the value was out of range. (Bug#22533)

ISNULL(DATE(NULL)) and ISNULL(CAST(NULL AS DATE)) erroneously returned false. (Bug#23938)

If a slave server closed its relay log (for example, due to an error during log rotation), the I/O thread did not recognize this and still tried to write to the log, causing a server crash. (Bug#10798)

Foreign key identifiers for InnoDB tables could not contain certain characters. (Bug#24299)

The number of setsockopt() calls performed for reads and writes to the network socket was reduced to decrease system call overhead. (Bug#22943)

ORDER BY on DOUBLE or DECIMAL values could change the set of rows returned by a query. (Bug#19690)

The InnoDB parser sometimes did not account for null bytes, causing spurious failure of some queries. (Bug#25596)

perror crashed on some platforms due to failure to handle a NULL pointer. (Bug#25344)

mysql_stmt_fetch() did an invalid memory deallocation when used with the embedded server. (Bug#25492)

mysqld_multi and mysqlaccess looked for option files in /etc even if the --sysconfdir option for configure had been given to specify a different directory. (Bug#24780)

The arguments of the ENCODE() and the DECODE() functions were not printed correctly, causing problems in the output of EXPLAIN EXTENDED. (Bug#23409)

A return value of -1 from user-defined handlers was not handled well and could result in conflicts with server code. (Bug#24987)

The server might fail to use an appropriate index for DELETE when ORDER BY, LIMIT, and a non-restricting WHERE are present. (Bug#17711)

For BOOLEAN mode full-text searches on non-indexed columns, NULL rows generated by a LEFT JOIN caused incorrect query results. (Bug#25637; see also Bug#14708)

SHOW COLUMNS reported some NOT NULL columns as NULL. (Bug#22377)

If an ORDER BY or GROUP BY list included a constant expression being optimized away and, at the same time, containing single-row subselects that return more that one row, no error was reported. If a query requires sorting by expressions containing single-row subselects that return more than one row, execution of the query may cause a server crash. (Bug#24653)

Attempts to access a MyISAM table with a corrupt column definition caused a server crash. (Bug#24401)

Accessing a fixed record format table with a crashed key definition results in server/myisamchk segmentation fault. (Bug#24855)

When opening a corrupted .frm file during a query, the server crashes. (Bug#24358)

If there was insufficient memory to store or update a blob record in a MyISAM table then the table will marked as crashed. (Bug#23196)

When updating a table that used a JOIN of the table itself (for example, when building trees) and the table was modified on one side of the expression, the table would either be reported as crashed or the wrong rows in the table would be updated. (Bug#21310)

No warning was issued for use of the DATA DIRECTORY or INDEX DIRECTORY table options on a platform that does not support them. (Bug#17498)

Hebrew-to-Unicode conversion failed for some characters. Definitions for the following Hebrew characters (as specified by the ISO/IEC 8859-8:1999) were added: LEFT-TO-RIGHT MARK (LRM), RIGHT-TO-LEFT MARK (RLM) (Bug#24037)

Certain joins using Range checked for each record in the query execution plan could cause the server to crash. (Bug#24776)

If there was insufficient memory available to mysqld, this could sometimes cause the server to hang during startup. (Bug#24751)

Optimizations that are legal only for subqueries without tables and WHERE conditions were applied for any subquery without tables. (Bug#24670)

NDB Cluster: The management client command node_id STATUS displayed the message Node node_id: not connected when node_id was not the node ID of a data node. (Bug#21715)

NDB Cluster (Cluster APIs): libndbclient.so was not versioned. (Bug#13522)

NDB Cluster: In some circumstances, shutting down the cluster could cause connected mysqld processes to crash. (Bug#25668)

mysqltest incorrectly tried to retrieve result sets for some queries where no result set was available. (Bug#19410)

mysqltest crashed with a stack overflow. (Bug#24498)

The server was built even when configure was run with the --without-server option. (Bug#23973)

A table created with the ROW_FORMAT = FIXED table option lost the option if an index was added or dropped with CREATE INDEX or DROP INDEX. (Bug#23404)

The BUILD/check-cpu script did not recognize Celeron processors. (Bug#20061)

InnoDB exhibited thread thrashing with more than 50 concurrent connections under an update-intensive workload. (Bug#22868)

InnoDB showed substandard performance with multiple queries running concurrently. (Bug#15815)

mysql_fix_privilege_tables did not handle a password containing embedded space or apostrophe characters. (Bug#17700)

Changing the value of MI_KEY_BLOCK_LENGTH in myisam.h and recompiling MySQL resulted in a myisamchk that saw existing MyISAM tables as corrupt. (Bug#22119)

SET lc_time_names = value allowed only exact literal values, not expression values. (Bug#22647)

Changes to the lc_time_names system variable were not replicated. (Bug#22645)

mysqldump --order-by-primary failed if the primary key name was an identifier that required quoting. (Bug#13926)

Re-execution of CREATE DATABASE, CREATE TABLE, and ALTER TABLE statements as prepared statements caused incorrect results or crashes. (Bug#22060)

The internal functions for table preparation, creation, and alteration were not re-execution friendly, causing problems in code that: repeatedly altered a table; repeatedly created and dropped a table; opened and closed a cursor on a table, altered the table, and then reopened the cursor. (Bug#4968, Bug#6895, Bug#19182, Bug#19733)

A deadlock could occur, with the server hanging on Closing tables, with a sufficient number of concurrent INSERT DELAYED, FLUSH TABLES, and ALTER TABLE operations. (Bug#23312)

Referencing an ambiguous column alias in an expression in the ORDER BY clause of a query caused the server to crash. (Bug#25427)

User-defined variables could consume excess memory, leading to a crash caused by the exhaustion of resources available to the MEMORY storage engine, due to the fact that this engine is used by MySQL for variable storage and intermediate results of GROUP BY queries. Where SET had been used, such a condition could instead give rise to the misleading error message You may only use constant expressions with SET, rather than Out of memory (Needed NNNNNN bytes). (Bug#23443)

InnoDB: During a restart of the MySQL Server that followed the creation of a temporary table using the InnoDB storage engine, MySQL failed to clean up in such a way that InnoDB still attempted to find the files associated with such tables. (Bug#20867)

A compressed MyISAM table that became corrupted could crash myisamchk and possibly the MySQL Server. (Bug#23139)

A crash of the MySQL Server could occur when unpacking a BLOB column from a row in a corrupted MyISAM table. This could happen when trying to repair a table using either REPAIR TABLE or myisamchk; it could also happen when trying to access such a “broken” row using statements like SELECT if the table was not marked as crashed. (Bug#22053)

Trailing spaces were not removed from Unicode CHAR column values when used in indexes. This resulted in excessive usage of storage space, and could affect the results of some ORDER BY queries that made use of such indexes.

Note: When upgrading, it is necessary to re-create any existing indexes on Unicode CHAR columns in order to take advantage of the fix. This can be done by using a REPAIR TABLE statement on each affected table.

(Bug#22052)

The stack size for NetWare binaries was increased to 128KB to prevent problems caused by insufficient stack size. (Bug#23504)

ALTER ENABLE KEYS or ALTER TABLE DISABLE KEYS combined with another ALTER TABLE option other than RENAME TO did nothing. In addition, if ALTER TABLE was used on a table having disabled keys, the keys of the resulting table were enabled. (Bug#24395)

Queries using a column alias in an expression as part of an ORDER BY clause failed, an example of such a query being SELECT mycol + 1 AS mynum FROM mytable ORDER BY 30 - mynum. (Bug#22457)

STR_TO_DATE() returned NULL if the format string contained a space following a non-format character. (Bug#22029)

Selecting into variables sometimes returned incorrect wrong results. (Bug#20836)

A server crash occurred when using LOAD DATA to load a table containing a NOT NULL spatial column, when the statement did not load the spatial column. Now a NULL supplied to NOT NULL column error occurs. (Bug#22372)

The --extern option for mysql-test-run.pl did not function correctly. (Bug#24354)

ALTER TABLE statements that performed both RENAME TO and {ENABLE|DISABLE} KEYS operations caused a server crash. (Bug#24089)

There was a race condition in the InnoDB fil_flush_file_spaces() function. (Bug#24089)

Some small double precision numbers (such as 1.00000001e-300) that should have been accepted were truncated to zero. (Bug#22129)

LAST_DAY('0000-00-00') could cause a server crash. (Bug#23653)

Through the C API, the member strings in MYSQL_FIELD for a query that contains expressions may return incorrect results. (Bug#21635)

IN() can return NULL, but did not signal that to the query processor, causing incorrect results for IS NULL operations. (Bug#17047)

The server could send incorrect column count information to the client for queries that produce a larger number of columns than can fit in a two-byte number. (Bug#19216)

SQL statements close to the size of max_allowed_packet could produce binary log events larger than max_allowed_packet that could not be read by slave servers. (Bug#19402)

If elements in a non-top-level IN subquery were accessed by an index and the subquery result set included a NULL value, the quantified predicate that contained the subquery was evaluated to NULL when it should return a non-NULL value. (Bug#23478)

Metadata for columns calculated from scalar subqueries was limited to integer, double, or string, even if the actual type of the column was different. (Bug#11032)

For ODBC compatibility, MySQL supports use of WHERE col_name IS NULL for DATE or DATETIME columns that are NOT NULL, to allow column values of '0000-00-00' or '0000-00-00 00:00:00' to be selected. However, this was not working for WHERE clauses in DELETE statements. (Bug#23412)

mysql did not check for errors when fetching data during result set printing. (Bug#22913)

Adding a day, month, or year interval to a DATE value produced a DATE, but adding a week interval produced a DATETIME value. Now all produce a DATE value. (Bug#21811)

For not-yet-authenticated connections, the Time column in SHOW PROCESSLIST was a random value rather than NULL. (Bug#23379)

The Handler_rollback status variable sometimes was incremented when no rollback had taken place. (Bug#22728)

Lack of validation for input and output TIME values resulted in several problems: SEC_TO_TIME() within subqueries incorrectly clipped large values; SEC_TO_TIME() treated BIGINT UNSIGNED values as signed; only truncation warnings were produced when both truncation and out-of-range TIME values occurred. (Bug#11655, Bug#20927)

Range searches on columns with an index prefix could miss records. (Bug#20732)

Transient errors in replication from master to slave may trigger multiple Got fatal error 1236: 'binlog truncated in the middle of event' errors on the slave. (Bug#4053)

If COMPRESS() returned NULL, subsequent invocations of COMPRESS() within a result set or within a trigger also returned NULL. (Bug#23254)

mysql would lose its connection to the server if its standard output was not writable. (Bug#17583)

mysql-test-run did not work correctly for RPM-based installations. (Bug#17194)

The return value from my_seek() was ignored. (Bug#22828)

MySQL would fail to build on the Alpha platform. (Bug#23256)