Hi!
In order to make prefix search better, and to bring all variants of
prefix search under one roof, we did some refactoring in the search
engine implementation, so that various prefix searches now use the same
code path and all use the SearchEngine class.
The changes are as follows:
SearchEngine gets the following new API functions:
* public function completionSearch( $search ) - implements prefix
completion search, returns SearchSuggestionSet
* public function completionSearchWithVariants( $search ) - implements
prefix completion search including variants handling, returns
SearchSuggestionSet.
* public function defaultPrefixSearch( $search ) - basic prefix search
without fuzzy matching, etc., to be used in scenarios like special pages
search, etc. Returns Title[].
The implementation does not have to implement all three methods
differently, they can all use the same code if needed.
The default implementation still supports the PrefixSearchBackend hook
but we plan to deprecate it, and the CirrusSearch implementation does
not use it anymore. Instead, there is a private function, protected
function completionSearchBackend( $search ), which implementations
(including CirrusSearch) should implement to provide search results.
SearchEngine implementations can make use of services provided by the
base SearchEngine including:
- namespace resolution and normalization. The
PrefixSearchExtractNamespace hook is still supported for engines wishing
to implement namespace lookup not featured in the standard implementation.
- fetching titles for result sets (the implementing engine does not have
to fetch titles from DB for suggestions)
- result reordering to ensure exact matches are on top
- basic prefix search implementation using the database
- Special: namespace search implementation
== Deprecations ==
We plan to deprecate the PrefixSearchBackend hook and classes
TitlePrefixSearch and StringPrefixSearch. We will keep those classes
around for basic search fallback implementation and for old extensions,
but no new code should be using these classes, instead they should use
SearchEngine APIs described above. Mediawiki code has already been fixed
to do that. Extensions implementing search engines should also extend
SearchEngine and override the APIs above. CirrusSearch is the example of
how to do it.
== Show me the code ==
The patches implementing the refactoring are linked from:
https://phabricator.wikimedia.org/T121430
Pretty version of the same:
https://www.mediawiki.org/wiki/User:Smalyshev_(WMF)/Suggester
If you have questions on this, please contact the Discovery team:
https://www.mediawiki.org/wiki/Wikimedia_Discovery#Communications
--
Stas Malyshev
smalyshev(a)wikimedia.org