Custom Indexer

You may write your own indexer and plug it into ke_search.

Feel free to use that extension as a kickstarter for your own custom indexer:

Hint

Make sure you fill $pid, $type, $language and (important) $additional_fields['orig_uid']. These fields are needed for the check if a content element already has been indexed. If you don't fill them, it may happen that only one content element of your specific type is indexed because all the elements are interpreted as the same record.
You don't need to fill $tags if you don't use faceting.
You don't need to fill $abstract, it will then generated automatically from $content.
You will have to fill $params if you want to link to a extension which expects a certain parameter, e.g. &tx_myextension_pi1[showUid]=123

Extending existing indexers

The indexers shipped with ke_search have hooks built in which allow you to modify the indexed data without writing a custom indexer. For example the page indexer provides the hook modifyPagesIndexEntry.

Adding hidden content

It is possible since version 4.5.0 to add content to the index which is searched but not shown in the result list. This is e.g. useful for Synonyms, different spellings, additional keywords and so on. The event ModifyFieldValuesBeforeStoringEvent in the class IndexerRunner is used for that.