Sphinx search backend returns inconsistent results for wildcard search

Discussed in phpBB • Sphinx search configuration

The default Sphinx config file provided with phpBB produces inconsistent results for a wildcard search with a two character word, i.e. te*.

A search for two characters can return matching results but adding a wildcard character to the same two characters returns no results. At a minimum the end user expects adding the wildcard would at least return the original search results for the case without the wildcard. 

This seems to be caused by the default Sphinx config file having min_word_len =2 and min_prefix_len = 3.  If min_prefix_len = min_word_len = 2, then the expected matching results are returned when adding a wildcard. 

This cannot be reproduced on www.phpbb.com/community as it would appear that min_prefix_len has been reduce to 2.