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// Copyright (C) 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ICING_SCORING_SCORER_H_
#define ICING_SCORING_SCORER_H_
#include <memory>
#include "icing/text_classifier/lib3/utils/base/statusor.h"
#include "icing/index/hit/doc-hit-info.h"
#include "icing/index/iterator/doc-hit-info-iterator.h"
#include "icing/proto/scoring.pb.h"
#include "icing/store/document-id.h"
#include "icing/store/document-store.h"
namespace icing {
namespace lib {
// Scorer calculates scores for documents.
class Scorer {
public:
virtual ~Scorer() = default;
// Factory function to create a Scorer which does not take ownership of any
// input components (DocumentStore), and all pointers must refer to valid
// objects that outlive the created Scorer instance. The default score will be
// returned only when the scorer fails to find or calculate a score for the
// document.
//
// Returns:
// A Scorer on success
// FAILED_PRECONDITION on any null pointer input
// INVALID_ARGUMENT if fails to create an instance
static libtextclassifier3::StatusOr<std::unique_ptr<Scorer>> Create(
const ScoringSpecProto& scoring_spec, double default_score,
const DocumentStore* document_store, const SchemaStore* schema_store);
// Returns a non-negative score of a document. The score can be a
// document-associated score which comes from the DocumentProto directly, an
// accumulated score, a relevance score, or even an inferred score. If it
// fails to find or calculate a score, the user-provided default score will be
// returned.
//
// Some examples of possible scores:
// 1. Document-associated scores: document score, creation timestamp score.
// 2. Accumulated scores: usage count score.
// 3. Inferred scores: a score calculated by a machine learning model.
// 4. Relevance score: computed as BM25F score.
//
// NOTE: This method is performance-sensitive as it's called for every
// potential result document. We're trying to avoid returning StatusOr<double>
// to save a little more time and memory.
virtual double GetScore(const DocHitInfo& hit_info,
const DocHitInfoIterator* query_it = nullptr) = 0;
// Currently only overriden by the RelevanceScoreScorer.
// NOTE: the query_term_iterators map must
// outlive the scorer, see bm25f-calculator for more details.
virtual void PrepareToScore(
std::unordered_map<std::string, std::unique_ptr<DocHitInfoIterator>>*
query_term_iterators) {}
};
} // namespace lib
} // namespace icing
#endif // ICING_SCORING_SCORER_H_
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