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Pagination and rescoring

Search-after pagination

Use the last hit from one page as the cursor for the next page:

var query = new TermQuery("body", "corpus");
var sort = SortField.Numeric("published", descending: true);

TopDocs first = searcher.Search(query, 25, sort);
TopDocs second = searcher.SearchAfter(first.ScoreDocs[^1], query, 25, sort);

Score order, document-ID order, single-field sorts and multi-field sorts are supported. The cursor must come from the same IndexSearcher snapshot and the same query and sort definition. SearchAfter counts every match but retains only the requested next-page candidates for segment-local query families. Queries that coordinate complete result sets across segments retain that coordination step.

Second-pass query rescoring

QueryRescorer reranks an existing candidate set without adding documents:

TopDocs firstPass = searcher.Search(new TermQuery("body", "search"), 100);
var rescorer = new QueryRescorer(
    new PhraseQuery("body", ["full", "text"]),
    firstPassWeight: 1,
    secondPassWeight: 3);

TopDocs reranked = rescorer.Rescore(searcher, firstPass, topN: 20);

Derive from QueryRescorer and override Combine when ranking needs a custom score combination.

Function values

DoubleValuesSource supplies numeric values from fields, constants or the current score. Sources compose without external dependencies:

DoubleValuesSource popularity =
    DoubleValuesSource.FromDoubleField("popularity")
        .Add(DoubleValuesSource.Constant(1));

var ranked = new FunctionScoreQuery(
    new TermQuery("body", "search"),
    popularity,
    ScoreMode.Multiply);

FunctionQuery matches all live documents and ranks them directly from a source. Custom sources can calculate freshness, distance or application signals by deriving from DoubleValuesSource.

  • SpanFirstQuery, SpanContainingQuery, SpanWithinQuery, FieldMaskingSpanQuery and SpanMultiTermQueryWrapper compose positional matching.
  • AnalysingQueryParser analyses literal portions of wildcard and prefix terms.
  • ComplexPhraseQueryParser turns multi-term and alternative clauses inside quotes into span queries.
  • TermsQuery accepts exact UTF-8 terms for large sets without converting them to strings during lookup.
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