Trait tantivy::query::Query [−] [src]

pub trait Query: Debug {
    fn weight(
        &self, 
        searcher: &Searcher, 
        scoring_enabled: bool
    ) -> Result<Box<Weight>>;

    fn count(&self, searcher: &Searcher) -> Result<usize> { ... }

    fn search(
        &self, 
        searcher: &Searcher, 
        collector: &mut Collector
    ) -> Result<TimerTree> { ... }
}

The Query trait defines a set of documents and a scoring method for those documents.

The Query trait is in charge of defining :

  • a set of documents
  • a way to score these documents

When performing a search, these documents will then be pushed to a Collector, which will in turn be in charge of deciding what to do with them.

Concretely, this scored docset is represented by the Scorer trait.

Because our index is actually split into segments, the query does not actually directly creates DocSet object. Instead, the query creates a Weight object for a given searcher.

The weight object, in turn, makes it possible to create a scorer for a specific SegmentReader.

So to sum it up :

  • a Query is recipe to define a set of documents as well the way to score them.
  • a Weight is this recipe tied to a specific Searcher. It may for instance hold statistics about the different term of the query. It is created by the query.
  • a Scorer is a cursor over the set of matching documents, for a specific SegmentReader. It is created by the Weight.

When implementing a new type of Query, it is normal to implement a dedicated Query, Weight and Scorer.

Required Methods

Create the weight associated to a query.

If scoring is not required, setting scoring_enabled to false can increase performances.

See Weight.

Provided Methods

Returns the number of documents matching the query.

Search works as follows :

First the weight object associated to the query is created.

Then, the query loops over the segments and for each segment :

  • setup the collector and informs it that the segment being processed has changed.
  • creates a Scorer object associated for this segment
  • iterate throw the matched documents and push them to the collector.

Implementors