Breaking: #102900 - Metaphone search removed from indexed_search

Description

The indexed_search based frontend functionality had a feature called "metaphone" to look for matches that "sound similar" to the given search word. This was available using the "Advanced search" interface, if it has not been disabled by an integrator. This feature has been removed.

This feature had so many issues that it was deemed unfixable:

• Most importantly, search results were bad. Even during dedicated testing, it was hard to retrieve any "similar sounding" results.
• The implementation was tailored for English language only, lacking support for any non-ASCII characters like umlauts. Sites with languages not based on single byte characters got even worse results.
• The code has been not maintained for about 15 years.
• The feature seems to be used so seldom, there does not seem to be a single extension that tries to fix at least the most important issues.
• There has been no issues reported about this broken feature over the years, except when it triggered crashes.

All in all it seems as if that feature was used extremely seldom, most likely because the results are so bad.

On a code level, the removal affects these areas:

• Class \TYPO3\CMS\IndexedSearch\Utility\DoubleMetaPhoneUtility has been removed.
• The "hook" $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['indexed_search']['metaphone'] to register an own "metaphone" solution has been removed.
• The extension configuration option enableMetaphoneSearch has been removed.
• The database columns index_fulltext.metaphonedata and index_words.metaphone have been removed.
• A couple of methods and properties in the @internal marked indexed_search classes have been removed and simplified.

Impact

Frontend users can no longer select the "Sounds like" option when searching the website. Backend users do not see statistics about this search variant in the backend module.

Affected installations

Websites with a search solution based on indexed_search with "metaphone" search being active in the extension configuration, and with users actively using the "metaphone" search feature.

Migration

No migration available. Sites that really need this feature should switch to a more sophisticated search solution.