A fuzzy query is a request to match terms that are reasonably similar to the query term. A wildcard is a strict form for specifying similarity, requiring the individual characters of the term to match precisely as written, while a fuzzy query allows characters to be shuffled, inserted, or deleted. Fuzzy query measures the editing distance, which is the number of characters which would have to be moved, inserted, or deleted to match the query term and then comparing that to half the length of the query term as a ratio. In other words, half as many characters as appear in the query term can be shuffled or changed in order to match the query term. Fuzzy query is good for matching similar terms as well as catching misspellings.
A fuzzy query is simply a single term (not a phrase) followed by a tilde ("~"). For example,
soap~ matches "soap", "soup", "soan", "loap", "sap", "asoap", and so on.
For cases in which you want to require greater or less similarity, an optional similarity ratio can be specified.
The similarity ratio is a float ratio written after the tilde, ranging from 0.0 to 0.999. The default is 0.5. Smaller ratios indicate that less similarity is required. Larger ratios indicate that greater similarity is required. Lucene does not support a ratio of 1.0 which would require no differences from the query term. Lucid will treat any value of 1.0 or greater as 0.999, which effectively requires an exact match unless the term is very long.
Lucene's implementation of fuzzy search is not very effective for very short terms (three characters or less) because it uses half of the term length as the maximum editing distance.
