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VladislavFitzVladislavFitz
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feat(search): Disjunctive Faceting (#802)
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‎Sources/AlgoliaSearchClient/Helpers/DisjunctiveFacetingHelper.swift‎

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//
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// DisjunctiveFacetingHelper.swift
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//
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//
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// Created by Vladislav Fitc on 19/10/2022.
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//
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import Foundation
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/// Helper making multiple queries for disjunctive faceting
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/// and merging the multiple search responses into a single one with
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/// combined facets information
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struct DisjunctiveFacetingHelper {
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let query: Query
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let refinements: [Attribute: [String]]
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let disjunctiveFacets: Set<Attribute>
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init(query: Query,
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refinements: [Attribute: [String]],
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disjunctiveFacets: Set<Attribute>) {
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self.query = query
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self.refinements = refinements
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self.disjunctiveFacets = disjunctiveFacets
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}
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/// Build filters SQL string from the provided refinements and disjunctive facets set
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func buildFilters(excluding excludedAttribute: Attribute?) -> String {
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String(
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refinements
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.sorted(by: { $0.key.rawValue < $1.key.rawValue })
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.filter { (name: Attribute, values: [String]) in
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name != excludedAttribute && !values.isEmpty
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}.map { (name: Attribute, values: [String]) in
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let facetOperator = disjunctiveFacets.contains(name) ? " OR " : " AND "
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let expression = values
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.map { value in """
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"\(name)":"\(value)"
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"""
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}
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.joined(separator: facetOperator)
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return "(\(expression))"
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}.joined(separator: " AND ")
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)
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}
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/// Get applied disjunctive facet values for provided attribute
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func appliedDisjunctiveFacetValues(for attribute: Attribute) -> Set<String> {
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guard disjunctiveFacets.contains(attribute) else {
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return []
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}
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return refinements[attribute].flatMap(Set.init) ?? []
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}
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/// Build search queries to fetch the necessary facets information for disjunctive faceting
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/// If the disjunctive facets set is empty, makes a single request with applied conjunctive filters
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func makeQueries() -> [Query] {
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var queries = [Query]()
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var mainQuery = query
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mainQuery.filters = buildFilters(excluding: .none)
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queries.append(mainQuery)
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disjunctiveFacets
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.sorted(by: { $0.rawValue < $1.rawValue })
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.forEach { disjunctiveFacet in
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var disjunctiveQuery = query
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disjunctiveQuery.facets = [disjunctiveFacet]
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disjunctiveQuery.filters = buildFilters(excluding: disjunctiveFacet)
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disjunctiveQuery.hitsPerPage = 0
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disjunctiveQuery.attributesToRetrieve = []
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disjunctiveQuery.attributesToHighlight = []
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disjunctiveQuery.attributesToSnippet = []
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disjunctiveQuery.analytics = false
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queries.append(disjunctiveQuery)
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}
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return queries
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}
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/// Merge received search responses into single one with combined facets information
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func mergeResponses(_ responses: [SearchResponse], keepSelectedEmptyFacets: Bool = true) throws -> SearchResponse {
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guard var mainResponse = responses.first else {
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throw DisjunctiveFacetingError.emptyResponses
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}
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let responsesForDisjunctiveFaceting = responses.dropFirst()
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var mergedDisjunctiveFacets = [Attribute: [Facet]]()
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var mergedFacetStats = mainResponse.facetStats ?? [:]
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var mergedExhaustiveFacetsCount = mainResponse.exhaustiveFacetsCount ?? true
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for result in responsesForDisjunctiveFaceting {
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// Merge facet values
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if let facetsPerAttribute = result.facets {
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for (attribute, facets) in facetsPerAttribute {
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// Complete facet values applied in the filters
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// but missed in the search response
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let missingFacets = appliedDisjunctiveFacetValues(for: attribute)
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.subtracting(facets.map(\.value))
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.map { Facet(value: $0, count: 0) }
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mergedDisjunctiveFacets[attribute] = facets + missingFacets
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}
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}
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// Merge facets stats
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if let facetStats = result.facetStats {
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mergedFacetStats.merge(facetStats) { _, last in last }
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}
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// If facet counts are not exhaustive, propagate this information to the main results.
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// Because disjunctive queries are less restrictive than the main query, it can happen that the main query
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// returns exhaustive facet counts, while the disjunctive queries do not.
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if let exhaustiveFacetsCount = result.exhaustiveFacetsCount {
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mergedExhaustiveFacetsCount = mergedExhaustiveFacetsCount && exhaustiveFacetsCount
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}
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}
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mainResponse.disjunctiveFacets = mergedDisjunctiveFacets
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mainResponse.facetStats = mergedFacetStats
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mainResponse.exhaustiveFacetsCount = mergedExhaustiveFacetsCount
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return mainResponse
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}
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}
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public enum DisjunctiveFacetingError: LocalizedError {
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case emptyResponses
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var localizedDescription: String {
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switch self {
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case .emptyResponses:
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return "Unexpected empty search responses list. At least one search responses might be present."
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}
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}
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}

‎Sources/AlgoliaSearchClient/Index/Index+Search.swift‎

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- Parameter strategy: The MultipleQueriesStrategy of the query.
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- Parameter requestOptions: Configure request locally with RequestOptions.
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- Parameter completion: Result completion
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- Returns: SearchesResponse object
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- Returns: Launched asynchronous operation
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*/
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@discardableResult func search(queries: [Query],
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strategy: MultipleQueriesStrategy = .none,
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return try transport.execute(command)
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}
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// MARK: - Disjunctive Faceting
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/**
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Method used for perform search with disjunctive facets.
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- Parameter query: The Query used to search.
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- Parameter refinements: Refinements to apply to the search in form of dictionary with
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facet attribute as a key and a list of facet values for the designated attribute
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- Parameter disjunctiveFacets: Set of facets attributes applied disjunctively (with OR operator)
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- Parameter keepSelectedEmptyFacets: Whether the selected facet values might be preserved even
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in case of their absence in the search response
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- Returns: SearchesResponse object
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*/
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func searchDisjunctiveFaceting(query: Query,
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refinements: [Attribute: [String]],
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disjunctiveFacets: Set<Attribute>,
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keepSelectedEmptyFacets: Bool = true) throws -> SearchResponse {
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let helper = DisjunctiveFacetingHelper(query: query,
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refinements: refinements,
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disjunctiveFacets: disjunctiveFacets)
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let queries = helper.makeQueries()
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let response = try search(queries: queries)
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return try helper.mergeResponses(response.results,
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keepSelectedEmptyFacets: keepSelectedEmptyFacets)
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}
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/**
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Method used for perform search with disjunctive facets.
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- Parameter query: The Query used to search.
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- Parameter refinements: Refinements to apply to the search in form of dictionary with
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facet attribute as a key and a list of facet values for the designated attribute
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- Parameter disjunctiveFacets: Set of facets attributes applied disjunctively (with OR operator)
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- Parameter keepSelectedEmptyFacets: Whether the selected facet values might be preserved even
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in case of their absence in the search response
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- Parameter completion: Result completion
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- Returns: Launched asynchronous operation
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*/
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func searchDisjunctiveFaceting(query: Query,
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refinements: [Attribute: [String]],
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disjunctiveFacets: Set<Attribute>,
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keepSelectedEmptyFacets: Bool = true,
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completion: @escaping ResultCallback<SearchResponse>) -> Operation & TransportTask {
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let helper = DisjunctiveFacetingHelper(query: query,
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refinements: refinements,
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disjunctiveFacets: disjunctiveFacets)
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let queries = helper.makeQueries()
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return search(queries: queries) { result in
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completion(result.flatMap { response in
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Result {
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try helper.mergeResponses(response.results,
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keepSelectedEmptyFacets: keepSelectedEmptyFacets)
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}
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})
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}
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}
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// MARK: - Browse
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/**

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