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.

Token filter plugins allow you to implement a custom tokenizer that creates tokens according to custom rules. There are two types:

• Index-time tokenizer declared by index_token_filter in table settings
• Query-time tokenizer declared by token_filter OPTION directive

In the text processing pipeline, token filters will run after the base tokenizer processing occurs (which processes the text from fields or queries and creates tokens out of them).

Index-time tokenizer is created by indexer when indexing source data into a table or by an RT table when processing INSERT or REPLACE statements.

Plugin is declared as library name:plugin name:optional string of settings. The init functions of the plugin can accept arbitrary settings that can be passed as a string in the format option1=value1;option2=value2;...

Example:

index_token_filter = my_lib.so:email_process:field=email;split=.io

The call workflow for index-time token filter is as follows:

1. XXX_init() gets called right after indexer creates token filter with an empty fields list and then after indexer gets the table schema with the actual fields list. It must return zero for successful initialization or an error description otherwise.
2. XXX_begin_document gets called only for RT table INSERT/REPLACE for every document. It must return zero for a successful call or an error description otherwise. Using OPTION token_filter_options, additional parameters/settings can be passed to the function.

   INSERT INTO rt (id, title) VALUES (1, 'some text corp@space.io') OPTION token_filter_options='.io'

3. XXX_begin_field gets called once for each field prior to processing the field with the base tokenizer, with the field number as its parameter.
4. XXX_push_token gets called once for each new token produced by the base tokenizer, with the source token as its parameter. It must return the token, count of extra tokens made by the token filter, and delta position for the token.
5. XXX_get_extra_token gets called multiple times in case XXX_push_token reports extra tokens. It must return the token and delta position for that extra token.
6. XXX_end_field gets called once right after the source tokens from the current field are processed.
7. XXX_deinit gets called at the very end of indexing.

The following functions are mandatory to be defined: XXX_begin_document, XXX_push_token, and XXX_get_extra_token.

Query-time tokenizer gets created on search each time full-text is invoked by every table involved.

The call workflow for query-time token filter is as follows:

1. XXX_init() gets called once per table prior to parsing the query with parameters - max token length and a string set by the token_filter option

   SELECT * FROM index WHERE MATCH ('test') OPTION token_filter='my_lib.so:query_email_process:io'

   It must return zero for successful initialization or error description otherwise.

2. XXX_push_token() gets called once for each new token produced by the base tokenizer with parameters: token produced by the base tokenizer, pointer to raw token at source query string, and raw token length. It must return the token and delta position for the token.
3. XXX_pre_morph() gets called once for the token right before it gets passed to the morphology processor with a reference to the token and stopword flag. It might set the stopword flag to mark the token as a stopword.
4. XXX_post_morph() gets called once for the token after it is processed by the morphology processor with a reference to the token and stopword flag. It might set the stopword flag to mark the token as a stopword. It must return a flag, the non-zero value of which means to use the token prior to morphology processing.
5. XXX_deinit() gets called at the very end of query processing.

Absence of the functions is tolerated.