Searching

There are two ways to query a FullTextIndex, searching with a query string and executing a manually constructed Query.

Searching with text

index.Search("find something");

This approach uses the IQueryParser implementation configured for the index to parse the query text into a Query object, which is then executed.

The default IQueryParser that is configured against an index parses the LIFTI query syntax, which is a fairly flexible way of expressing a query. If you want to swap out this parser with a custom implementation, you can do so when building the index using WithQueryParser option.

Searching with a Query

You can manually construct a Query using any combination of IQueryParts, but take care to normalize any text to match in the same way that it has been indexed. You can do this using either the IIndexTokenizer for the index, or if specific tokenization rules have been configured for a field, then the tokenizer for that field:

var tokenizer = index.DefaultTokenizer;
var query = new Query(
    new AndQueryPart(
        new ExactWordQueryPart(tokenizer.Normalize("hello")), 
        new ExactWordQueryPart(tokenizer.Normalize("there"))));

Obtaining query execution plans

By specifying QueryExecutionOptions.IncludeExecutionPlan when searching, LIFTI will collect timing information during the execution of the various query parts:

index.Search("find something", QueryExecutionOptions.IncludeExecutionPlan);

This enables ISearchResults.GetExecutionPlan to return the actual execution plan for the query. If QueryExecutionOptions.IncludeExecutionPlan is not specified, GetExecutionPlan returns a placeholder execution plan.

See Understanding LIFTI query execution plans for more details.