Log Message:
Changes 5.5.28:

The internal interface of the Thread Pool plugin has changed. Old versions of \ 
the plugin will work with current versions of the server, but versions of the \ 
server older than 5.5.28 will not work with current versions of the plugin.

Bugs Fixed

InnoDB: Certain information_schema tables originally introduced in MySQL 5.6 are \ 
now also available in MySQL 5.5 and MySQL 5.1: INNODB_BUFFER_PAGE, \ 
INNODB_BUFFER_PAGE_LRU, and INNODB_BUFFER_POOL_STATS.

InnoDB: When a SELECT ... FOR UPDATE, UPDATE, or other SQL statement scanned \ 
rows in an InnoDB table using a < or <= operator in a WHERE clause, the \ 
next row after the affected range could also be locked. This issue could cause a \ 
lock wait timeout for a row that was not expected to be locked. The issue \ 
occurred under various isolation levels, such as READ COMMITTED and REPEATABLE \ 
READ.

Partitioning: For tables using PARTITION BY HASH or PARTITION BY KEY, when the \ 
partition pruning mechanism encountered a multi-range list or inequality using a \ 
column from the partitioning key, it continued with the next partitioning column \ 
and tried to use it for pruning, even if the previous column could not be used. \ 
This caused partitions which possibly matched one or more of the previous \ 
partitioning columns to be pruned away, leaving partitions that matched only the \ 
last column of the partitioning key.

This issue was triggered when both of the following conditions were met:

The columns making up the table's partitioning key were used in the same order \ 
as in the partitioning key definition by a SELECT statement's WHERE clause as in \ 
the column definitions;

The WHERE condition used with the last column of the partitioning key was \ 
satisfied only by a single value, while the condition testing some previous \ 
column from the partitioning key was satisfied by a range of values.

An example of a statement creating a partitioned table and a query against this \ 
for which the issue described above occurred is shown here:

CREATE TABLE t1 (
  c1 INT,
  c2 INT,
  PRIMARY KEY(c2, c1)
) PARTITION BY KEY()  # Use primary key as partitioning key
  PARTITIONS 2;

SELECT * FROM t1 WHERE c2 = 2 AND c1 <> 2;
This issue is resolved by ensuring that partition pruning skips any remaining \ 
partitioning key columns once a partition key column that cannot be used in \ 
pruning is encountered.

Partitioning: The buffer for the row currently read from each partition used for \ 
sorted reads was allocated on open and freed only when the partitioning handler \ 
was closed or destroyed. For SELECT statements on tables with many partitions \ 
and large rows, this could cause the server to use excessive amounts of memory.

This issue has been addressed by allocating buffers for reads from partitioned \ 
tables only when they are needed and freeing them immediately once they are no \ 
longer needed. As part of this fix, memory is now allocated for reading from \ 
rows only in partitions that have not been pruned (see Section 18.4, \ 
“Partition Pruning”).

Replication: On 64-bit Windows platforms, values greater than 4G for the \ 
max_binlog_cache_size and max_binlog_stmt_cache_size system variables were \ 
truncated to 4G. This caused LOAD DATA INFILE to fail when trying to load a file \ 
larger than 4G in size, even when max_binlog_cache_size was set to a value \ 
greater than this.

Replication: In master-master replication with --log-slave-updates enabled, \ 
setting a user variable and then performing inserts using this variable caused \ 
the Exec_master_log_position column in the output of SHOW SLAVE STATUS not to be \ 
updated.

The RPM spec file now also runs the test suite on the new binaries, before \ 
packaging them.

The libmysqlclient_r client library exported symbols from yaSSL that conflict \ 
with OpenSSL. If a program linked against that library and libcurl, it could \ 
crash with a segmentation fault.

The argument for LIMIT must be an integer, but if the argument was given by a \ 
placeholder in a prepared statement, the server did not reject noninteger values \ 
such as '5'.

The Thread Pool plugin did not respect the wait_timeout timeout for client sessions.

CHECK TABLE and REPAIR TABLE could crash if a key definition differed in the \ 
.frm and .MYI files of a MyISAM table. Now the server produces an error.

A query for a FEDERATED table could return incorrect results when the underlying \ 
table had a compound index on two columns and the query included an AND \ 
condition on the columns.

mysqlhotcopy failed for databases containing views.

The argument to the --ssl-key option was not verified to exist and be a valid \ 
key. The resulting connection used SSL, but the key was not used.

Adding a LIMIT clause to a query containing GROUP BY and ORDER BY could cause \ 
the optimizer to choose an incorrect index for processing the query, and return \ 
more rows than required.

mysqlbinlog did not accept input on the standard input when the standard input \ 
was a pipe.