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account_search_query_builder.rb 4.91 KiB
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# frozen_string_literal: true
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class AccountSearchQueryBuilder
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  DISALLOWED_TSQUERY_CHARACTERS = /['?\\:‘’]/.freeze
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  LANGUAGE     = Arel::Nodes.build_quoted('simple').freeze
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  EMPTY_STRING = Arel::Nodes.build_quoted('').freeze
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  WEIGHT_A     = Arel::Nodes.build_quoted('A').freeze
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  WEIGHT_B     = Arel::Nodes.build_quoted('B').freeze
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  WEIGHT_C     = Arel::Nodes.build_quoted('C').freeze
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  FIELDS = {
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    display_name: { weight: WEIGHT_A }.freeze,
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    username:     { weight: WEIGHT_B }.freeze,
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    domain:       { weight: WEIGHT_C, nullable: true }.freeze,
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  }.freeze
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  RANK_NORMALIZATION = 32
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  DEFAULT_OPTIONS = {
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    limit: 10,
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    only_following: false,
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  }.freeze
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  # @param [String] terms
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  # @param [Hash] options
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  # @option [Account] :account
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  # @option [Boolean] :only_following
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  # @option [Integer] :limit
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  # @option [Integer] :offset
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  def initialize(terms, options = {})
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    @terms   = terms
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    @options = DEFAULT_OPTIONS.merge(options)
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  end
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  # @return [ActiveRecord::Relation]
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  def build
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    search_scope.tap do |scope|
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      scope.merge!(personalization_scope) if with_account?
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      if with_account? && only_following?
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        scope.merge!(only_following_scope)
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        scope.with!(first_degree_definition) # `merge!` does not handle `with`
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      end
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    end
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  end
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  # @return [Array<Account>]
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  def results
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    build.to_a
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  end
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  private
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  def search_scope
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    Account.select(projections)
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           .where(match_condition)
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           .searchable
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           .includes(:account_stat)
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           .order(rank: :desc)
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           .limit(limit)
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           .offset(offset)
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  end
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  def personalization_scope
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    join_condition = accounts_table.join(follows_table, Arel::Nodes::OuterJoin)
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                                   .on(accounts_table.grouping(accounts_table[:id].eq(follows_table[:account_id]).and(follows_table[:target_account_id].eq(account.id))).or(accounts_table.grouping(accounts_table[:id].eq(follows_table[:target_account_id]).and(follows_table[:account_id].eq(account.id)))))
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                                   .join_sources
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    Account.joins(join_condition)
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.group(accounts_table[:id]) end def only_following_scope Account.where(accounts_table[:id].in(first_degree_table.project('*'))) end def first_degree_definition target_account_ids_query = follows_table.project(follows_table[:target_account_id]).where(follows_table[:account_id].eq(account.id)) account_id_query = Arel::SelectManager.new.project(account.id) Arel::Nodes::As.new( first_degree_table, target_account_ids_query.union(:all, account_id_query) ) end def projections rank_column = begin if with_account? weighted_tsrank_template.as('rank') else tsrank_template.as('rank') end end [all_columns, rank_column] end def all_columns accounts_table[Arel.star] end def match_condition Arel::Nodes::InfixOperation.new('@@', tsvector_template, tsquery_template) end def tsrank_template @tsrank_template ||= Arel::Nodes::NamedFunction.new('ts_rank_cd', [tsvector_template, tsquery_template, RANK_NORMALIZATION]) end def weighted_tsrank_template @weighted_tsrank_template ||= Arel::Nodes::Multiplication.new(weight, tsrank_template) end def weight Arel::Nodes::Addition.new(follows_table[:id].count, 1) end def tsvector_template return @tsvector_template if defined?(@tsvector_template) vectors = FIELDS.keys.map do |column| options = FIELDS[column] vector = accounts_table[column] vector = Arel::Nodes::NamedFunction.new('coalesce', [vector, EMPTY_STRING]) if options[:nullable] vector = Arel::Nodes::NamedFunction.new('to_tsvector', [LANGUAGE, vector]) Arel::Nodes::NamedFunction.new('setweight', [vector, options[:weight]]) end @tsvector_template = Arel::Nodes::Grouping.new(vectors.reduce { |memo, vector| Arel::Nodes::Concat.new(memo, vector) }) end def query_vector @query_vector ||= Arel::Nodes::NamedFunction.new('to_tsquery', [LANGUAGE, tsquery_template]) end def sanitized_terms
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@sanitized_terms ||= @terms.gsub(DISALLOWED_TSQUERY_CHARACTERS, ' ') end def tsquery_template return @tsquery_template if defined?(@tsquery_template) terms = [ Arel::Nodes.build_quoted("' "), Arel::Nodes.build_quoted(sanitized_terms), Arel::Nodes.build_quoted(" '"), Arel::Nodes.build_quoted(':*'), ] @tsquery_template = Arel::Nodes::NamedFunction.new('to_tsquery', [LANGUAGE, terms.reduce { |memo, term| Arel::Nodes::Concat.new(memo, term) }]) end def account @options[:account] end def with_account? account.present? end def limit @options[:limit] end def offset @options[:offset] end def only_following? @options[:only_following] end def accounts_table Account.arel_table end def follows_table Follow.arel_table end def first_degree_table Arel::Table.new(:first_degree) end end