Sphinx is a free open-source SQL full-text search engine, and quite useful for fast full-text search. If you get the error
ERROR: index 'main': sql_fetch_row: Lost connection to MySQL server during query
during indexing of a large database with Sphinx (large means more than 500.000 rows in a table), then it may help to increase the MySQL “Read timeout” from 30 to 3600, for example with the MySQL administrator. “Read timeout” is the number of seconds to wait for more data from a connection before aborting the read.