It will be almost impossible to use utf8mb4 with XWiki, because of the
terrible way mysql is designed. Here's the reason why:

mysql imposes several hard limits on the maximum size of several things:
length of indexes, length of rows. These lengths, unfortunately, are not
computed as the maximum size of the actual data, but of the theoretical
data that could be placed in there. This means that the size of a
VARCHAR(255) isn't 255 bytes, but 255 chars * maximum number of bytes
that such a char could have (3 for utf8, 4 for utf8mb4).

You could make it work if you change the schema to reduce the length of
several fields, but you would do that at your own risk.

On 04/06/2016 08:58 PM, Debajit Adhikary wrote:
> Some more information:
> On my Mac, when I try to set up XWiki with MySQL, I ran the following:
> # Install mysql and start
>     brew update
>     brew install mysql
>     mysql.server start
>     # Now I can connect as "mysql -uroot"
> # Create a new MySQL database for XWiki
> # see
>     mysql -u root -e "create database xwiki default character set utf8mb4
> collate utf8mb4_unicode_ci"
>     mysql -u root -e "grant all privileges on *.* to xwiki@localhost
> identified by 'xwiki'"
> # Configure hibernate.cfg.xml
> # This is only the mysql section
>     <property name="connection.url">jdbc:mysql://localhost/xwiki</property>
>     <property name="connection.username">xwiki</property>
>     <property name="connection.password">xwiki</property>
>     <property
> name="connection.driver_class">com.mysql.jdbc.Driver</property>
>     <property
> name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
>     <property name="connection.useUnicode">true</property>
>     <property name="connection.characterEncoding">UTF-8</property>
>     <property name="dbcp.poolPreparedStatements">true</property>
>     <property name="dbcp.maxOpenPreparedStatements">20</property>
>     <mapping resource="xwiki.hbm.xml"/>
>     <mapping resource="feeds.hbm.xml"/>
>     <mapping resource="activitystream.hbm.xml"/>
>     <mapping resource="instance.hbm.xml"/>
>     <mapping resource="mailsender.hbm.xml"/>
> Now when I start XWiki, I get the error:
> com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:
> Row size too large. The maximum row size for the used table type, not
> counting BLOBs, is 65535. This includes storage overhead, check the manual.
> You have to change some columns to TEXT or BLOBs
> It looks like whatever creates the XWiki tables is not handling utf8mb4
> (see also ).
> On Wed, Apr 6, 2016 at 5:17 PM, Debajit Adhikary <>
> wrote:
>> I have an XWiki installation, and I noticed that emoji's were not getting
>> saved correctly and were rendering as question marks in XWiki. This is
>> caused by MySQL's default encoding which is "utf8" and not "utf8mb4"
>> (4-byte UTF to store the full unicode character set)
>> To fix this, I am in the process of converting all my MySQL database
>> tables into utf8mb4 encoding, which is turning out to be quite a lot of
>> manual work.
>> When XWiki creates the database tables for MySQL, can it use utf8mb4
>> encoding by default? Is this something I could open a bug request for?
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Sergiu Dumitriu
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