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MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
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Attempts to assign value to a table column from trigger by using
NEW.column_name pseudo-variable might result in garbled data.
That happened when:
- the column had a BLOB-based type (e.g. TEXT)
and
- the value being assigned was retrieved from stored routine variable
of the same type.
The problem was that BLOB values were not copied correctly in this
case. Instead of doing a copy of a real value, the value's representation
in record buffer was copied. This representation is essentially a
pointer to a buffer associated with the virtual table for routine
variables where the real value is stored. Since this buffer got
freed once trigger was left or could have changed its contents when
new value was assigned to corresponding routine variable such a shallow
copying resulted in garbled data in NEW.colum_name column.
It worked in 5.1 due to a subtle bug in create_virtual_tmp_table():
- in 5.1 create_virtual_tmp_table() returned a table which
had db_low_byte_first == false.
- in 5.5 and up create_virtual_tmp_table() returns a table which
has db_low_byte_first == true.
Actually, db_low_byte_first == false only for ISAM storage engine,
which was deprecated and removed in 5.0.
Having db_low_byte_first == false led to getting false in the
complex condition for the 2nd "if" in field_conv(), which in turn
led to copy-blob-behavior as a fall-back strategy:
- to->table->s->db_low_byte_first was true (correct value)
- from->table->s->db_low_byte_first was false (incorrect value)
In 5.5 and up that condition is true, which means blob-values are
not copied.
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| sql | ||
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| vio | ||
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| configure.cmake | ||
| COPYING | ||
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| INSTALL-WIN-SOURCE | ||
| README | ||
| VERSION | ||
MySQL Server 5.5 This is a release of MySQL, a dual-license SQL database server. For the avoidance of doubt, this particular copy of the software is released under the version 2 of the GNU General Public License. MySQL is brought to you by Oracle. Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. License information can be found in the COPYING file. MySQL FOSS License Exception We want free and open source software applications under certain licenses to be able to use specified GPL-licensed MySQL client libraries despite the fact that not all such FOSS licenses are compatible with version 2 of the GNU General Public License. Therefore there are special exceptions to the terms and conditions of the GPLv2 as applied to these client libraries, which are identified and described in more detail in the FOSS License Exception at <http://www.mysql.com/about/legal/licensing/foss-exception.html>. This distribution may include materials developed by third parties. For license and attribution notices for these materials, please refer to the documentation that accompanies this distribution (see the "Licenses for Third-Party Components" appendix) or view the online documentation at <http://dev.mysql.com/doc/>. GPLv2 Disclaimer For the avoidance of doubt, except that if any license choice other than GPL or LGPL is available it will apply instead, Oracle elects to use only the General Public License version 2 (GPLv2) at this time for any software where a choice of GPL license versions is made available with the language indicating that GPLv2 or any later version may be used, or where a choice of which version of the GPL is applied is otherwise unspecified. For further information about MySQL or additional documentation, see: - The latest information about MySQL: http://www.mysql.com - The current MySQL documentation: http://dev.mysql.com/doc Some Reference Manual sections of special interest: - If you are migrating from an older version of MySQL, please read the "Upgrading from..." section. - To see what MySQL can do, take a look at the features section. - For installation instructions, see the Installing and Upgrading chapter. - For the new features/bugfix history, see the MySQL Change History appendix. You can browse the MySQL Reference Manual online or download it in any of several formats at the URL given earlier in this file. Source distributions include a local copy of the manual in the Docs directory.