The basic structure of the Information Schema plugins in similar to that of Daemon plugins. They need to be declared with mysql_declare_plugin, and can have status and system variables. The initialization function, though, is a requirement for them, not an option, as this is the function where we define a new Information Schema table and tell MySQL what should happen when it is queried.
Just like with any other plugin type we use a macro to declare a plugin. This time we set the plugin type to MYSQL_INFORMATION_SCHEMA_PLUGIN. An example of the definition may look like this:
mysql_declare_plugin(mysql_is_my_plugin)
{
MYSQL_INFORMATION_SCHEMA_PLUGIN,
&mysql_is_my_plugin,
"IS_MY_PLUGIN",
"Andrew Hutchings ([email protected])",
"An information schema plugin",
PLUGIN_LICENSE_GPL,
is_my_plugin_init,
is_my_plugin_deinit,
0x0010,
NULL,
NULL,
NULL
}
The differences start when we get to the initialization function...