MySQL 5.7 Release Notes
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The FEDERATED storage engine lets you access data
from a remote MySQL database without using replication or cluster
technology. Querying a local FEDERATED table
automatically pulls the data from the remote (federated) tables. No
data is stored on the local tables.
To include the FEDERATED storage engine if you
build MySQL from source, invoke CMake with the
-DWITH_FEDERATED_STORAGE_ENGINE
option.
The FEDERATED storage engine is not enabled by
default in the running server; to enable
FEDERATED, you must start the MySQL server binary
using the --federated option.
To examine the source for the FEDERATED engine,
look in the storage/federated directory of a
MySQL source distribution.
The result the entire db will fail to load and the following error will appear in the logs:
110318 21:37:23 [ERROR] /usr/local/libexec/mysqld: unknown option '--federated'
This in turn means that an upgrade from 5.x needs to be done in two steps if you have federated tables. Once with --skip-grant-tables and without --federated, the once without --skip-grant-tables and with --federated.
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