RELOAD PLUGINS FROM SONAME 'plugin_library'

Reloads all plugins (UDFs, rankers, etc.) from a given library. In a sense, the reload process is transactional, ensuring that:

1. all plugins are successfully updated to their new versions;
2. the update is atomic, meaning all plugins are replaced simultaneously. This atomicity ensures that queries using multiple functions from a reloaded library will never mix old and new versions.

During the RELOAD, the set of plugins is guaranteed to be consistent; they will either be all old or all new.

The reload process is also seamless, as some version of a reloaded plugin will always be available for concurrent queries, without any temporary disruptions. This is an improvement over using a pair of DROP and CREATE statements for reloading. With those, there is a brief window between the DROP and the subsequent CREATE during which queries technically refer to an unknown plugin and will therefore fail.

If there's any failure, RELOAD PLUGINS does nothing, retains the old plugins, and reports an error.

On Windows, overwriting or deleting a DLL library currently in use can be problematic. However, you can still rename it, place a new version under the old name, and then RELOAD will work. After a successful reload, you'll also be able to delete the renamed old library.

mysql> RELOAD PLUGINS FROM SONAME 'udfexample.dll';
Query OK, 0 rows affected (0.00 sec)

Ranker plugins let you implement a custom ranker that receives all the occurrences of the keywords matched in the document, and computes a WEIGHT() value. They can be called as follows:

SELECT id, attr1 FROM test WHERE match('hello') OPTION ranker=myranker('option1=1');

The call workflow proceeds as follows:

1. XXX_init() is invoked once per query per table, at the very beginning. Several query-wide options are passed to it via a SPH_RANKER_INIT structure, including the user options strings (for instance, "option1=1" in the example above).
2. XXX_update() is called multiple times for each matched document, with every matched keyword occurrence provided as its parameter, a SPH_RANKER_HIT structure. The occurrences within each document are guaranteed to be passed in ascending order of hit->hit_pos values.
3. XXX_finalize() is called once for each matched document when there are no more keyword occurrences. It must return the WEIGHT() value. This function is the only mandatory one.
4. XXX_deinit() is invoked once per query, at the very end.