Search query extender and helper functions.
Performs a query on the full-text search index for a word or words.
This query is used by search plugins that use the search index (not all search plugins do, as some use a different searching mechanism). It assumes you have set up a query on the {search_index} table with alias 'i', and will only work if the user is searching for at least one "positive" keyword or phrase.
For efficiency, users of this query can run the prepareAndNormalize() method to