Query parser configuration

Configuring the default LIFTI QueryParser

FullTextIndexBuilder<TKey> WithQueryParser(Func<QueryParserBuilder, QueryParserBuilder> optionsBuilder)

By default LIFTI parses query text using the LIFTI query syntax. The behavior of the parser can be tweaked using this overload.

Providing a complete IQueryParser implementation

FullTextIndexBuilder<TKey> WithQueryParser(IQueryParser queryParser)

Allows you to provide your own implementation of IQueryParser capable of parsing text into an IQuery.

To see an example of a custom IQueryParser implementation, see this blog post.

QueryParserBuilder options

WithDefaultJoiningOperator

QueryParserBuilder.WithDefaultJoiningOperator(QueryTermJoinOperatorKind joiningOperator) The default joining operator for queries is and. This means that without explicitly adding in an & or | to a LIFTI query, & will be assumed, and all search terms must match in a document. This method allows you to choose between and and or as the default joining operator.

AssumeFuzzySearchTerms

QueryParserBuilder.AssumeFuzzySearchTerms() When used, uses fuzzy matching for any parsed search terms that don’t contain wildcard operators, i.e. you don’t need to prefix search terms with ?.

WithFuzzySearchDefaults

QueryParserBuilder.WithFuzzySearchDefaults(ushort maxEditDistance, ushort maxSequentialEdits) Configures the default parameters for a fuzzy search when not provided explicitly as part of the query. This overload provides static values to use for the maximum edit distance and maximum sequential edits for a fuzzy search.

QueryParserBuilder.WithFuzzySearchDefaults(Func<int, ushort> maxEditDistance, Func<int, ushort> maxSequentialEdits) Configures the default parameters for a fuzzy search when not provided explicitly as part of the query. This overload allows for the maximum edit distance and maximum sequential edits for a fuzzy search to be calculated from the length of a search term.

If either of these functions returns zero, then fuzzy matching will be disabled for the search term.

By default maxEditDistance is calculated as termLength / 3, which means that fuzzy matching will be disabled for any search term less than 2 characters. The default for maxSequentialEdits is Max(1, termLength / 4), which means that no matter how short the search term, at least one sequential edit is allowed.

See Fuzzy Matching.

WithQueryParserFactory

QueryParserBuilder.WithQueryParserFactory(Func<QueryParserOptions, IQueryParser>) Given a QueryParserOptions, creates the implementation of IQueryParser. You can use this to provide a custom query parsing strategy.

Example usage

var index = new FullTextIndexBuilder<int>()
    .WithQueryParser(o => o.AssumeFuzzySearch())
    .Build();