A binary upgrade or downgrade is one that installs one version of MySQL “in place” over an existing version, without dumping and reloading tables:
Stop the server for the existing version if it is running.
Install a different version of MySQL. This is an upgrade if the new version is higher than the original version, a downgrade if the version is lower.
Start the server for the new version.
In many cases, the tables from the previous version of MySQL can be used without problem by the new version. However, sometimes changes occur that require tables or table indexes to be rebuilt, as described in this section. If you have tables that are affected by any of the issues described here, rebuild the tables or indexes as necessary using the instructions given in Section 2.11.4, “Rebuilding or Repairing Tables or Indexes”.
As of MySQL 5.6.4, MySQL permits fractional seconds for
TIMESTAMP column values. As a
result, encoding and storage requirements for these temporal
column types differ in tables created in MySQL 5.6.4 and later.
This incompatibility is described in
Section 22.214.171.124, “Changes Affecting Upgrades to MySQL 5.6”. When upgrading
to MySQL 5.6.4 or later, be aware that
CHECK TABLE ... FOR
UPGRADE does not report temporal columns that use the
pre-MySQL 5.6.4 format (Bug #73008, Bug #18985579). In MySQL
5.6.24, two new system variables,
show_old_temporals, were added to
provide control over temporal column upgrades (Bug #72997, Bug
In MySQL 5.6.3, the length limit for index prefix keys is
increased from 767 bytes to 3072 bytes, for
InnoDB tables using
Section 14.8.8, “Limits on InnoDB Tables” for details. This change is
also backported to MySQL 5.5.14. If you downgrade from one of
these releases or higher, to an earlier release with a lower
length limit, the index prefix keys could be truncated at 767
bytes or the downgrade could fail. This issue could only occur if
the configuration option
innodb_large_prefix was enabled
on the server being downgraded.
If you perform a binary upgrade without dumping and reloading
tables, you cannot upgrade directly from MySQL 4.1 to 5.1 or
higher. This occurs due to an incompatible change in the
MyISAM table index format in MySQL 5.0. Upgrade
from MySQL 4.1 to 5.0 and repair all
tables. Then upgrade from MySQL 5.0 to 5.1 and check and repair
Modifications to the handling of character sets or collations might change the character sort order, which causes the ordering of entries in any index that uses an affected character set or collation to be incorrect. Such changes result in several possible problems:
Comparison results that differ from previous results
Inability to find some index values due to misordered index entries
CHECK TABLEreports as being in need of repair
The solution to these problems is to rebuild any indexes that use an affected character set or collation, either by dropping and re-creating the indexes, or by dumping and reloading the entire table. In some cases, it is possible to alter affected columns to use a different collation. For information about rebuilding indexes, see Section 2.11.4, “Rebuilding or Repairing Tables or Indexes”.
To check whether a table has indexes that must be rebuilt, consult the following list. It indicates which versions of MySQL introduced character set or collation changes that require indexes to be rebuilt. Each entry indicates the version in which the change occurred and the character sets or collations that the change affects. If the change is associated with a particular bug report, the bug number is given.
The list applies both for binary upgrades and downgrades. For example, Bug #27877 was fixed in MySQL 5.1.24, so it applies to upgrades from versions older than 5.1.24 to 5.1.24 or higher, and to downgrades from 5.1.24 or newer to versions older than 5.1.24.
In many cases, you can use
CHECK TABLE ... FOR
UPGRADE to identify tables for which index rebuilding is
required. It will report this message:
Table upgrade required. Please do "REPAIR TABLE `tbl_name`" or dump/reload to fix it!
In these cases, you can also use mysqlcheck
--check-upgrade or mysql_upgrade,
CHECK TABLE. However,
the use of
CHECK TABLE applies only
after upgrades, not downgrades. Also,
TABLE is not applicable to all storage engines. For
details about which storage engines
TABLE supports, see Section 126.96.36.199, “CHECK TABLE Syntax”.
These changes cause index rebuilding to be necessary:
MySQL 5.1.24 (Bug #27877)
Affects indexes that use the
ucs2_general_cicollation for columns that contain
'ß'LATIN SMALL LETTER SHARP S (German). The bug fix corrected an error in the original collations but introduced an incompatibility such that
'ß'compares equal to characters with which it previously compared different.
Affected tables can be detected by
CHECK TABLE ... FOR UPGRADEas of MySQL 5.1.30 (see Bug #40053).
A workaround for this issue is implemented as of MySQL 5.1.62, 5.5.21, and 5.6.5. The workaround involves altering affected columns to use the
ucs2_general_mysql500_cicollations, which preserve the original pre-5.1.24 ordering of