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Reciprocal Rank Fusion (RRF) normalization technique in hybrid query (o…
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…pensearch-project#874)


* initial commit of RRF

Signed-off-by: Isaac Johnson <[email protected]>

Co-authored-by: Varun Jain <[email protected]>
Signed-off-by: Martin Gaievski <[email protected]>
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2 people authored and martin-gaievski committed Nov 25, 2024
1 parent 4875dd5 commit 4cc2141
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),

## [Unreleased 2.x](https://github.com/opensearch-project/neural-search/compare/2.18...2.x)
### Features
- Implement Reciprocal Rank Fusion score normalization/combination technique in hybrid query ([#874](https://github.com/opensearch-project/neural-search/pull/874))
### Enhancements
### Bug Fixes
### Infrastructure
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import org.opensearch.neuralsearch.ml.MLCommonsClientAccessor;
import org.opensearch.neuralsearch.processor.NeuralQueryEnricherProcessor;
import org.opensearch.neuralsearch.processor.NeuralSparseTwoPhaseProcessor;
import org.opensearch.neuralsearch.processor.NormalizationProcessor;
import org.opensearch.neuralsearch.processor.NormalizationProcessorWorkflow;
import org.opensearch.neuralsearch.processor.SparseEncodingProcessor;
import org.opensearch.neuralsearch.processor.TextEmbeddingProcessor;
import org.opensearch.neuralsearch.processor.TextChunkingProcessor;
import org.opensearch.neuralsearch.processor.TextImageEmbeddingProcessor;
import org.opensearch.neuralsearch.processor.RRFProcessor;
import org.opensearch.neuralsearch.processor.NormalizationProcessor;
import org.opensearch.neuralsearch.processor.combination.ScoreCombinationFactory;
import org.opensearch.neuralsearch.processor.combination.ScoreCombiner;
import org.opensearch.neuralsearch.processor.factory.TextChunkingProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.NormalizationProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.RerankProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.SparseEncodingProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.TextEmbeddingProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.TextImageEmbeddingProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.RRFProcessorFactory;
import org.opensearch.neuralsearch.processor.factory.NormalizationProcessorFactory;
import org.opensearch.neuralsearch.processor.normalization.ScoreNormalizationFactory;
import org.opensearch.neuralsearch.processor.normalization.ScoreNormalizer;
import org.opensearch.neuralsearch.processor.rerank.RerankProcessor;
Expand Down Expand Up @@ -154,7 +156,9 @@ public Map<String, org.opensearch.search.pipeline.Processor.Factory<SearchPhaseR
) {
return Map.of(
NormalizationProcessor.TYPE,
new NormalizationProcessorFactory(normalizationProcessorWorkflow, scoreNormalizationFactory, scoreCombinationFactory)
new NormalizationProcessorFactory(normalizationProcessorWorkflow, scoreNormalizationFactory, scoreCombinationFactory),
RRFProcessor.TYPE,
new RRFProcessorFactory(normalizationProcessorWorkflow, scoreNormalizationFactory, scoreCombinationFactory)
);
}

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/*
* Copyright OpenSearch Contributors
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.neuralsearch.processor;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.NonNull;
import org.opensearch.neuralsearch.processor.combination.ScoreCombinationTechnique;
import org.opensearch.neuralsearch.processor.normalization.ScoreNormalizationTechnique;
import org.opensearch.search.fetch.FetchSearchResult;
import org.opensearch.search.query.QuerySearchResult;

import java.util.List;
import java.util.Optional;

/**
* DTO object to hold data in NormalizationProcessorWorkflow class
* in NormalizationProcessorWorkflow.
*/
@AllArgsConstructor
@Builder
@Getter
public class NormalizationExecuteDTO {
@NonNull
private List<QuerySearchResult> querySearchResults;
@NonNull
private Optional<FetchSearchResult> fetchSearchResultOptional;
@NonNull
private ScoreNormalizationTechnique normalizationTechnique;
@NonNull
private ScoreCombinationTechnique combinationTechnique;
}
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Expand Up @@ -58,7 +58,15 @@ public <Result extends SearchPhaseResult> void process(
}
List<QuerySearchResult> querySearchResults = getQueryPhaseSearchResults(searchPhaseResult);
Optional<FetchSearchResult> fetchSearchResult = getFetchSearchResults(searchPhaseResult);
normalizationWorkflow.execute(querySearchResults, fetchSearchResult, normalizationTechnique, combinationTechnique);
// Builds data transfer object to pass into execute, DTO has nullable field for rankConstant which
// is only used for RRF technique
NormalizationExecuteDTO normalizationExecuteDTO = NormalizationExecuteDTO.builder()
.querySearchResults(querySearchResults)
.fetchSearchResultOptional(fetchSearchResult)
.normalizationTechnique(normalizationTechnique)
.combinationTechnique(combinationTechnique)
.build();
normalizationWorkflow.execute(normalizationExecuteDTO);
}

@Override
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Expand Up @@ -47,26 +47,31 @@ public class NormalizationProcessorWorkflow {

/**
* Start execution of this workflow
* @param querySearchResults input data with QuerySearchResult from multiple shards
* @param normalizationTechnique technique for score normalization
* @param combinationTechnique technique for score combination
* @param normalizationExecuteDTO contains querySearchResults input data with QuerySearchResult
* from multiple shards, fetchSearchResultOptional, normalizationTechnique technique for score normalization
* combinationTechnique technique for score combination, and nullable rankConstant only used in RRF technique
*/
public void execute(
final List<QuerySearchResult> querySearchResults,
final Optional<FetchSearchResult> fetchSearchResultOptional,
final ScoreNormalizationTechnique normalizationTechnique,
final ScoreCombinationTechnique combinationTechnique
) {
public void execute(final NormalizationExecuteDTO normalizationExecuteDTO) {
final List<QuerySearchResult> querySearchResults = normalizationExecuteDTO.getQuerySearchResults();
final Optional<FetchSearchResult> fetchSearchResultOptional = normalizationExecuteDTO.getFetchSearchResultOptional();
final ScoreNormalizationTechnique normalizationTechnique = normalizationExecuteDTO.getNormalizationTechnique();
final ScoreCombinationTechnique combinationTechnique = normalizationExecuteDTO.getCombinationTechnique();
// save original state
List<Integer> unprocessedDocIds = unprocessedDocIds(querySearchResults);

// pre-process data
log.debug("Pre-process query results");
List<CompoundTopDocs> queryTopDocs = getQueryTopDocs(querySearchResults);

// Data transfer object for score normalization used to pass nullable rankConstant which is only used in RRF
NormalizeScoresDTO normalizeScoresDTO = NormalizeScoresDTO.builder()
.queryTopDocs(queryTopDocs)
.normalizationTechnique(normalizationTechnique)
.build();

// normalize
log.debug("Do score normalization");
scoreNormalizer.normalizeScores(queryTopDocs, normalizationTechnique);
scoreNormalizer.normalizeScores(normalizeScoresDTO);

CombineScoresDto combineScoresDTO = CombineScoresDto.builder()
.queryTopDocs(queryTopDocs)
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/*
* Copyright OpenSearch Contributors
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.neuralsearch.processor;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.NonNull;
import org.opensearch.neuralsearch.processor.normalization.ScoreNormalizationTechnique;

import java.util.List;

/**
* DTO object to hold data required for score normalization.
*/
@AllArgsConstructor
@Builder
@Getter
public class NormalizeScoresDTO {
@NonNull
private List<CompoundTopDocs> queryTopDocs;
@NonNull
private ScoreNormalizationTechnique normalizationTechnique;
}
139 changes: 139 additions & 0 deletions src/main/java/org/opensearch/neuralsearch/processor/RRFProcessor.java
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/*
* Copyright OpenSearch Contributors
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.neuralsearch.processor;

import static org.opensearch.neuralsearch.search.util.HybridSearchResultFormatUtil.isHybridQueryStartStopElement;

import java.util.stream.Collectors;

import java.util.List;
import java.util.Objects;
import java.util.Optional;

import lombok.Getter;
import org.opensearch.neuralsearch.processor.combination.ScoreCombinationTechnique;
import org.opensearch.neuralsearch.processor.normalization.ScoreNormalizationTechnique;
import org.opensearch.search.fetch.FetchSearchResult;
import org.opensearch.search.query.QuerySearchResult;

import org.opensearch.action.search.QueryPhaseResultConsumer;
import org.opensearch.action.search.SearchPhaseContext;
import org.opensearch.action.search.SearchPhaseName;
import org.opensearch.action.search.SearchPhaseResults;
import org.opensearch.search.SearchPhaseResult;
import org.opensearch.search.internal.SearchContext;
import org.opensearch.search.pipeline.SearchPhaseResultsProcessor;

import lombok.AllArgsConstructor;
import lombok.extern.log4j.Log4j2;

/**
* Processor for implementing reciprocal rank fusion technique on post
* query search results. Updates query results with
* normalized and combined scores for next phase (typically it's FETCH)
* by using ranks from individual subqueries to calculate 'normalized'
* scores before combining results from subqueries into final results
*/
@Log4j2
@AllArgsConstructor
public class RRFProcessor implements SearchPhaseResultsProcessor {
public static final String TYPE = "score-ranker-processor";

@Getter
private final String tag;
@Getter
private final String description;
private final ScoreNormalizationTechnique normalizationTechnique;
private final ScoreCombinationTechnique combinationTechnique;
private final NormalizationProcessorWorkflow normalizationWorkflow;

/**
* Method abstracts functional aspect of score normalization and score combination. Exact methods for each processing stage
* are set as part of class constructor
* @param searchPhaseResult {@link SearchPhaseResults} DTO that has query search results. Results will be mutated as part of this method execution
* @param searchPhaseContext {@link SearchContext}
*/
@Override
public <Result extends SearchPhaseResult> void process(
final SearchPhaseResults<Result> searchPhaseResult,
final SearchPhaseContext searchPhaseContext
) {
if (shouldSkipProcessor(searchPhaseResult)) {
log.debug("Query results are not compatible with RRF processor");
return;
}
List<QuerySearchResult> querySearchResults = getQueryPhaseSearchResults(searchPhaseResult);
Optional<FetchSearchResult> fetchSearchResult = getFetchSearchResults(searchPhaseResult);

// make data transfer object to pass in, execute will get object with 4 or 5 fields, depending
// on coming from NormalizationProcessor or RRFProcessor
NormalizationExecuteDTO normalizationExecuteDTO = NormalizationExecuteDTO.builder()
.querySearchResults(querySearchResults)
.fetchSearchResultOptional(fetchSearchResult)
.normalizationTechnique(normalizationTechnique)
.combinationTechnique(combinationTechnique)
.build();
normalizationWorkflow.execute(normalizationExecuteDTO);
}

@Override
public SearchPhaseName getBeforePhase() {
return SearchPhaseName.QUERY;
}

@Override
public SearchPhaseName getAfterPhase() {
return SearchPhaseName.FETCH;
}

@Override
public String getType() {
return TYPE;
}

@Override
public boolean isIgnoreFailure() {
return false;
}

private <Result extends SearchPhaseResult> boolean shouldSkipProcessor(SearchPhaseResults<Result> searchPhaseResult) {
if (Objects.isNull(searchPhaseResult) || !(searchPhaseResult instanceof QueryPhaseResultConsumer queryPhaseResultConsumer)) {
return true;
}

return queryPhaseResultConsumer.getAtomicArray().asList().stream().filter(Objects::nonNull).noneMatch(this::isHybridQuery);
}

/**
* Return true if results are from hybrid query.
* @param searchPhaseResult
* @return true if results are from hybrid query
*/
private boolean isHybridQuery(final SearchPhaseResult searchPhaseResult) {
// check for delimiter at the end of the score docs.
return Objects.nonNull(searchPhaseResult.queryResult())
&& Objects.nonNull(searchPhaseResult.queryResult().topDocs())
&& Objects.nonNull(searchPhaseResult.queryResult().topDocs().topDocs.scoreDocs)
&& searchPhaseResult.queryResult().topDocs().topDocs.scoreDocs.length > 0
&& isHybridQueryStartStopElement(searchPhaseResult.queryResult().topDocs().topDocs.scoreDocs[0]);
}

private <Result extends SearchPhaseResult> List<QuerySearchResult> getQueryPhaseSearchResults(
final SearchPhaseResults<Result> results
) {
return results.getAtomicArray()
.asList()
.stream()
.map(result -> result == null ? null : result.queryResult())
.collect(Collectors.toList());
}

private <Result extends SearchPhaseResult> Optional<FetchSearchResult> getFetchSearchResults(
final SearchPhaseResults<Result> searchPhaseResults
) {
Optional<Result> optionalFirstSearchPhaseResult = searchPhaseResults.getAtomicArray().asList().stream().findFirst();
return optionalFirstSearchPhaseResult.map(SearchPhaseResult::fetchResult);
}
}
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/*
* Copyright OpenSearch Contributors
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.neuralsearch.processor.combination;

import lombok.ToString;
import lombok.extern.log4j.Log4j2;

import java.util.Map;

@Log4j2
/**
* Abstracts combination of scores based on reciprocal rank fusion algorithm
*/
@ToString(onlyExplicitlyIncluded = true)
public class RRFScoreCombinationTechnique implements ScoreCombinationTechnique {
@ToString.Include
public static final String TECHNIQUE_NAME = "rrf";

// Not currently using weights for RRF, no need to modify or verify these params
public RRFScoreCombinationTechnique(final Map<String, Object> params, final ScoreCombinationUtil combinationUtil) {}

@Override
public float combine(final float[] scores) {
float sumScores = 0.0f;
for (float score : scores) {
sumScores += score;
}
return sumScores;
}
}
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Expand Up @@ -25,7 +25,9 @@ public class ScoreCombinationFactory {
HarmonicMeanScoreCombinationTechnique.TECHNIQUE_NAME,
params -> new HarmonicMeanScoreCombinationTechnique(params, scoreCombinationUtil),
GeometricMeanScoreCombinationTechnique.TECHNIQUE_NAME,
params -> new GeometricMeanScoreCombinationTechnique(params, scoreCombinationUtil)
params -> new GeometricMeanScoreCombinationTechnique(params, scoreCombinationUtil),
RRFScoreCombinationTechnique.TECHNIQUE_NAME,
params -> new RRFScoreCombinationTechnique(params, scoreCombinationUtil)
);

/**
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Expand Up @@ -25,7 +25,7 @@
@Log4j2
class ScoreCombinationUtil {
private static final String PARAM_NAME_WEIGHTS = "weights";
private static final float DELTA_FOR_SCORE_ASSERTION = 0.01f;
private static final float DELTA_FOR_WEIGHTS_ASSERTION = 0.01f;

/**
* Get collection of weights based on user provided config
Expand Down Expand Up @@ -117,7 +117,7 @@ protected void validateIfWeightsMatchScores(final float[] scores, final List<Flo
* @param weightsList
*/
private void validateWeights(final List<Float> weightsList) {
boolean isOutOfRange = weightsList.stream().anyMatch(weight -> !Range.between(0.0f, 1.0f).contains(weight));
boolean isOutOfRange = weightsList.stream().anyMatch(weight -> !Range.of(0.0f, 1.0f).contains(weight));
if (isOutOfRange) {
throw new IllegalArgumentException(
String.format(
Expand All @@ -128,7 +128,7 @@ private void validateWeights(final List<Float> weightsList) {
);
}
float sumOfWeights = weightsList.stream().reduce(0.0f, Float::sum);
if (!DoubleMath.fuzzyEquals(1.0f, sumOfWeights, DELTA_FOR_SCORE_ASSERTION)) {
if (!DoubleMath.fuzzyEquals(1.0f, sumOfWeights, DELTA_FOR_WEIGHTS_ASSERTION)) {
throw new IllegalArgumentException(
String.format(
Locale.ROOT,
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