glitchier-soc/lib/mastodon/maintenance_cli.rb

# frozen_string_literal: true

require 'tty-prompt'
require_relative '../../config/boot'
require_relative '../../config/environment'
require_relative 'cli_helper'

module Mastodon
  class MaintenanceCLI < Thor
    include CLIHelper

    def self.exit_on_failure?
      true
    end

    MIN_SUPPORTED_VERSION = 2019_10_01_213028
    MAX_SUPPORTED_VERSION = 2022_11_04_133904

    # Stubs to enjoy ActiveRecord queries while not depending on a particular
    # version of the code/database

    class Status < ApplicationRecord; end
    class StatusPin < ApplicationRecord; end
    class Poll < ApplicationRecord; end
    class Report < ApplicationRecord; end
    class Tombstone < ApplicationRecord; end
    class Favourite < ApplicationRecord; end
    class Follow < ApplicationRecord; end
    class FollowRequest < ApplicationRecord; end
    class Block < ApplicationRecord; end
    class Mute < ApplicationRecord; end
    class AccountIdentityProof < ApplicationRecord; end
    class AccountModerationNote < ApplicationRecord; end
    class AccountPin < ApplicationRecord; end
    class ListAccount < ApplicationRecord; end
    class PollVote < ApplicationRecord; end
    class Mention < ApplicationRecord; end
    class AccountDomainBlock < ApplicationRecord; end
    class AnnouncementReaction < ApplicationRecord; end
    class FeaturedTag < ApplicationRecord; end
    class CustomEmoji < ApplicationRecord; end
    class CustomEmojiCategory < ApplicationRecord; end
    class Bookmark < ApplicationRecord; end
    class WebauthnCredential < ApplicationRecord; end
    class FollowRecommendationSuppression < ApplicationRecord; end
    class CanonicalEmailBlock < ApplicationRecord; end
    class Appeal < ApplicationRecord; end
    class Webhook < ApplicationRecord; end

    class PreviewCard < ApplicationRecord
      self.inheritance_column = false
    end

    class MediaAttachment < ApplicationRecord
      self.inheritance_column = nil
    end

    class AccountStat < ApplicationRecord
      belongs_to :account, inverse_of: :account_stat
    end

    # Dummy class, to make migration possible across version changes
    class Account < ApplicationRecord
      has_one :user, inverse_of: :account
      has_one :account_stat, inverse_of: :account

      scope :local, -> { where(domain: nil) }

      def local?
        domain.nil?
      end

      def acct
        local? ? username : "#{username}@#{domain}"
      end

      # This is a duplicate of the AccountMerging concern because we need it to
      # be independent from code version.
      def merge_with!(other_account)
        # Since it's the same remote resource, the remote resource likely
        # already believes we are following/blocking, so it's safe to
        # re-attribute the relationships too. However, during the presence
        # of the index bug users could have *also* followed the reference
        # account already, therefore mass update will not work and we need
        # to check for (and skip past) uniqueness errors

        owned_classes = [
          Status, StatusPin, MediaAttachment, Poll, Report, Tombstone, Favourite,
          Follow, FollowRequest, Block, Mute,
          AccountModerationNote, AccountPin, AccountStat, ListAccount,
          PollVote, Mention
        ]
        owned_classes << AccountDeletionRequest if ActiveRecord::Base.connection.table_exists?(:account_deletion_requests)
        owned_classes << AccountNote if ActiveRecord::Base.connection.table_exists?(:account_notes)
        owned_classes << FollowRecommendationSuppression if ActiveRecord::Base.connection.table_exists?(:follow_recommendation_suppressions)
        owned_classes << AccountIdentityProof if ActiveRecord::Base.connection.table_exists?(:account_identity_proofs)
        owned_classes << Appeal if ActiveRecord::Base.connection.table_exists?(:appeals)

        owned_classes.each do |klass|
          klass.where(account_id: other_account.id).find_each do |record|
            record.update_attribute(:account_id, id)
          rescue ActiveRecord::RecordNotUnique
            next
          end
        end

        target_classes = [Follow, FollowRequest, Block, Mute, AccountModerationNote, AccountPin]
        target_classes << AccountNote if ActiveRecord::Base.connection.table_exists?(:account_notes)

        target_classes.each do |klass|
          klass.where(target_account_id: other_account.id).find_each do |record|
            record.update_attribute(:target_account_id, id)
          rescue ActiveRecord::RecordNotUnique
            next
          end
        end

        if ActiveRecord::Base.connection.table_exists?(:canonical_email_blocks)
          CanonicalEmailBlock.where(reference_account_id: other_account.id).find_each do |record|
            record.update_attribute(:reference_account_id, id)
          end
        end

        if ActiveRecord::Base.connection.table_exists?(:appeals)
          Appeal.where(account_warning_id: other_account.id).find_each do |record|
            record.update_attribute(:account_warning_id, id)
          end
        end
      end
    end

    class User < ApplicationRecord
      belongs_to :account, inverse_of: :user
    end

    desc 'fix-duplicates', 'Fix duplicates in database and rebuild indexes'
    long_desc <<~LONG_DESC
      Delete or merge duplicate accounts, statuses, emojis, etc. and rebuild indexes.

      This is useful if your database indexes are corrupted because of issues such as https://wiki.postgresql.org/wiki/Locale_data_changes

      Mastodon has to be stopped to run this task, which will take a long time and may be destructive.
    LONG_DESC
    def fix_duplicates
      @prompt = TTY::Prompt.new

      if ActiveRecord::Migrator.current_version < MIN_SUPPORTED_VERSION
        @prompt.error 'Your version of the database schema is too old and is not supported by this script.'
        @prompt.error 'Please update to at least Mastodon 3.0.0 before running this script.'
        exit(1)
      elsif ActiveRecord::Migrator.current_version > MAX_SUPPORTED_VERSION
        @prompt.warn 'Your version of the database schema is more recent than this script, this may cause unexpected errors.'
        exit(1) unless @prompt.yes?('Continue anyway? (Yes/No)')
      end

      if Sidekiq::ProcessSet.new.any?
        @prompt.error 'It seems Sidekiq is running. All Mastodon processes need to be stopped when using this script.'
        exit(1)
      end

      @prompt.warn 'This task will take a long time to run and is potentially destructive.'
      @prompt.warn 'Please make sure to stop Mastodon and have a backup.'
      exit(1) unless @prompt.yes?('Continue? (Yes/No)')

      deduplicate_users!
      deduplicate_account_domain_blocks!
      deduplicate_account_identity_proofs!
      deduplicate_announcement_reactions!
      deduplicate_conversations!
      deduplicate_custom_emojis!
      deduplicate_custom_emoji_categories!
      deduplicate_domain_allows!
      deduplicate_domain_blocks!
      deduplicate_unavailable_domains!
      deduplicate_email_domain_blocks!
      deduplicate_media_attachments!
      deduplicate_preview_cards!
      deduplicate_statuses!
      deduplicate_accounts!
      deduplicate_tags!
      deduplicate_webauthn_credentials!
      deduplicate_webhooks!

      Scenic.database.refresh_materialized_view('instances', concurrently: true, cascade: false) if ActiveRecord::Migrator.current_version >= 2020_12_06_004238
      Rails.cache.clear

      @prompt.say 'Finished!'
    end

    private

    def deduplicate_accounts!
      remove_index_if_exists!(:accounts, 'index_accounts_on_username_and_domain_lower')

      @prompt.say 'Deduplicating accounts… for local accounts, you will be asked to chose which account to keep unchanged.'

      find_duplicate_accounts.each do |row|
        accounts = Account.where(id: row['ids'].split(',')).to_a

        if accounts.first.local?
          deduplicate_local_accounts!(accounts)
        else
          deduplicate_remote_accounts!(accounts)
        end
      end

      @prompt.say 'Restoring index_accounts_on_username_and_domain_lower…'
      if ActiveRecord::Migrator.current_version < 2020_06_20_164023
        ActiveRecord::Base.connection.add_index :accounts, 'lower (username), lower(domain)', name: 'index_accounts_on_username_and_domain_lower', unique: true
      else
        ActiveRecord::Base.connection.add_index :accounts, "lower (username), COALESCE(lower(domain), '')", name: 'index_accounts_on_username_and_domain_lower', unique: true
      end

      @prompt.say 'Reindexing textual indexes on accounts…'
      ActiveRecord::Base.connection.execute('REINDEX INDEX search_index;')
      ActiveRecord::Base.connection.execute('REINDEX INDEX index_accounts_on_uri;')
      ActiveRecord::Base.connection.execute('REINDEX INDEX index_accounts_on_url;')
    end

    def deduplicate_users!
      remove_index_if_exists!(:users, 'index_users_on_confirmation_token')
      remove_index_if_exists!(:users, 'index_users_on_email')
      remove_index_if_exists!(:users, 'index_users_on_remember_token')
      remove_index_if_exists!(:users, 'index_users_on_reset_password_token')

      @prompt.say 'Deduplicating user records…'

      # Deduplicating email
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM users GROUP BY email HAVING count(*) > 1").each do |row|
        users = User.where(id: row['ids'].split(',')).sort_by(&:updated_at).reverse
        ref_user = users.shift
        @prompt.warn "Multiple users registered with e-mail address #{ref_user.email}."
        @prompt.warn "e-mail will be disabled for the following accounts: #{user.map(&:account).map(&:acct).join(', ')}"
        @prompt.warn 'Please reach out to them and set another address with `tootctl account modify` or delete them.'

        i = 0
        users.each do |user|
          user.update!(email: "#{i} " + user.email)
        end
      end

      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM users WHERE confirmation_token IS NOT NULL GROUP BY confirmation_token HAVING count(*) > 1").each do |row|
        users = User.where(id: row['ids'].split(',')).sort_by(&:created_at).reverse.drop(1)
        @prompt.warn "Unsetting confirmation token for those accounts: #{users.map(&:account).map(&:acct).join(', ')}"

        users.each do |user|
          user.update!(confirmation_token: nil)
        end
      end

      if ActiveRecord::Migrator.current_version < 2022_01_18_183010
        ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM users WHERE remember_token IS NOT NULL GROUP BY remember_token HAVING count(*) > 1").each do |row|
          users = User.where(id: row['ids'].split(',')).sort_by(&:updated_at).reverse.drop(1)
          @prompt.warn "Unsetting remember token for those accounts: #{users.map(&:account).map(&:acct).join(', ')}"

          users.each do |user|
            user.update!(remember_token: nil)
          end
        end
      end

      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM users WHERE reset_password_token IS NOT NULL GROUP BY reset_password_token HAVING count(*) > 1").each do |row|
        users = User.where(id: row['ids'].split(',')).sort_by(&:updated_at).reverse.drop(1)
        @prompt.warn "Unsetting password reset token for those accounts: #{users.map(&:account).map(&:acct).join(', ')}"

        users.each do |user|
          user.update!(reset_password_token: nil)
        end
      end

      @prompt.say 'Restoring users indexes…'
      ActiveRecord::Base.connection.add_index :users, ['confirmation_token'], name: 'index_users_on_confirmation_token', unique: true
      ActiveRecord::Base.connection.add_index :users, ['email'], name: 'index_users_on_email', unique: true
      ActiveRecord::Base.connection.add_index :users, ['remember_token'], name: 'index_users_on_remember_token', unique: true if ActiveRecord::Migrator.current_version < 2022_01_18_183010

      if ActiveRecord::Migrator.current_version < 2022_03_10_060641
        ActiveRecord::Base.connection.add_index :users, ['reset_password_token'], name: 'index_users_on_reset_password_token', unique: true
      else
        ActiveRecord::Base.connection.add_index :users, ['reset_password_token'], name: 'index_users_on_reset_password_token', unique: true, where: 'reset_password_token IS NOT NULL', opclass: :text_pattern_ops
      end
    end

    def deduplicate_account_domain_blocks!
      remove_index_if_exists!(:account_domain_blocks, 'index_account_domain_blocks_on_account_id_and_domain')

      @prompt.say 'Removing duplicate account domain blocks…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM account_domain_blocks GROUP BY account_id, domain HAVING count(*) > 1").each do |row|
        AccountDomainBlock.where(id: row['ids'].split(',').drop(1)).delete_all
      end

      @prompt.say 'Restoring account domain blocks indexes…'
      ActiveRecord::Base.connection.add_index :account_domain_blocks, %w(account_id domain), name: 'index_account_domain_blocks_on_account_id_and_domain', unique: true
    end

    def deduplicate_account_identity_proofs!
      return unless ActiveRecord::Base.connection.table_exists?(:account_identity_proofs)

      remove_index_if_exists!(:account_identity_proofs, 'index_account_proofs_on_account_and_provider_and_username')

      @prompt.say 'Removing duplicate account identity proofs…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM account_identity_proofs GROUP BY account_id, provider, provider_username HAVING count(*) > 1").each do |row|
        AccountIdentityProof.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring account identity proofs indexes…'
      ActiveRecord::Base.connection.add_index :account_identity_proofs, %w(account_id provider provider_username), name: 'index_account_proofs_on_account_and_provider_and_username', unique: true
    end

    def deduplicate_announcement_reactions!
      return unless ActiveRecord::Base.connection.table_exists?(:announcement_reactions)

      remove_index_if_exists!(:announcement_reactions, 'index_announcement_reactions_on_account_id_and_announcement_id')

      @prompt.say 'Removing duplicate account identity proofs…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM announcement_reactions GROUP BY account_id, announcement_id, name HAVING count(*) > 1").each do |row|
        AnnouncementReaction.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring announcement_reactions indexes…'
      ActiveRecord::Base.connection.add_index :announcement_reactions, %w(account_id announcement_id name), name: 'index_announcement_reactions_on_account_id_and_announcement_id', unique: true
    end

    def deduplicate_conversations!
      remove_index_if_exists!(:conversations, 'index_conversations_on_uri')

      @prompt.say 'Deduplicating conversations…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM conversations WHERE uri IS NOT NULL GROUP BY uri HAVING count(*) > 1").each do |row|
        conversations = Conversation.where(id: row['ids'].split(',')).sort_by(&:id).reverse

        ref_conversation = conversations.shift

        conversations.each do |other|
          merge_conversations!(ref_conversation, other)
          other.destroy
        end
      end

      @prompt.say 'Restoring conversations indexes…'
      if ActiveRecord::Migrator.current_version < 2022_03_07_083603
        ActiveRecord::Base.connection.add_index :conversations, ['uri'], name: 'index_conversations_on_uri', unique: true
      else
        ActiveRecord::Base.connection.add_index :conversations, ['uri'], name: 'index_conversations_on_uri', unique: true, where: 'uri IS NOT NULL', opclass: :text_pattern_ops
      end
    end

    def deduplicate_custom_emojis!
      remove_index_if_exists!(:custom_emojis, 'index_custom_emojis_on_shortcode_and_domain')

      @prompt.say 'Deduplicating custom_emojis…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM custom_emojis GROUP BY shortcode, domain HAVING count(*) > 1").each do |row|
        emojis = CustomEmoji.where(id: row['ids'].split(',')).sort_by(&:id).reverse

        ref_emoji = emojis.shift

        emojis.each do |other|
          merge_custom_emojis!(ref_emoji, other)
          other.destroy
        end
      end

      @prompt.say 'Restoring custom_emojis indexes…'
      ActiveRecord::Base.connection.add_index :custom_emojis, %w(shortcode domain), name: 'index_custom_emojis_on_shortcode_and_domain', unique: true
    end

    def deduplicate_custom_emoji_categories!
      remove_index_if_exists!(:custom_emoji_categories, 'index_custom_emoji_categories_on_name')

      @prompt.say 'Deduplicating custom_emoji_categories…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM custom_emoji_categories GROUP BY name HAVING count(*) > 1").each do |row|
        categories = CustomEmojiCategory.where(id: row['ids'].split(',')).sort_by(&:id).reverse

        ref_category = categories.shift

        categories.each do |other|
          merge_custom_emoji_categories!(ref_category, other)
          other.destroy
        end
      end

      @prompt.say 'Restoring custom_emoji_categories indexes…'
      ActiveRecord::Base.connection.add_index :custom_emoji_categories, ['name'], name: 'index_custom_emoji_categories_on_name', unique: true
    end

    def deduplicate_domain_allows!
      remove_index_if_exists!(:domain_allows, 'index_domain_allows_on_domain')

      @prompt.say 'Deduplicating domain_allows…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM domain_allows GROUP BY domain HAVING count(*) > 1").each do |row|
        DomainAllow.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring domain_allows indexes…'
      ActiveRecord::Base.connection.add_index :domain_allows, ['domain'], name: 'index_domain_allows_on_domain', unique: true
    end

    def deduplicate_domain_blocks!
      remove_index_if_exists!(:domain_blocks, 'index_domain_blocks_on_domain')

      @prompt.say 'Deduplicating domain_allows…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM domain_blocks GROUP BY domain HAVING count(*) > 1").each do |row|
        domain_blocks = DomainBlock.where(id: row['ids'].split(',')).by_severity.reverse.to_a

        reject_media = domain_blocks.any?(&:reject_media?)
        reject_reports = domain_blocks.any?(&:reject_reports?)

        reference_block = domain_blocks.shift

        private_comment = domain_blocks.reduce(reference_block.private_comment.presence) { |a, b| a || b.private_comment.presence }
        public_comment  = domain_blocks.reduce(reference_block.public_comment.presence)  { |a, b| a || b.public_comment.presence }

        reference_block.update!(reject_media: reject_media, reject_reports: reject_reports, private_comment: private_comment, public_comment: public_comment)

        domain_blocks.each(&:destroy)
      end

      @prompt.say 'Restoring domain_blocks indexes…'
      ActiveRecord::Base.connection.add_index :domain_blocks, ['domain'], name: 'index_domain_blocks_on_domain', unique: true
    end

    def deduplicate_unavailable_domains!
      return unless ActiveRecord::Base.connection.table_exists?(:unavailable_domains)

      remove_index_if_exists!(:unavailable_domains, 'index_unavailable_domains_on_domain')

      @prompt.say 'Deduplicating unavailable_domains…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM unavailable_domains GROUP BY domain HAVING count(*) > 1").each do |row|
        UnavailableDomain.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring domain_allows indexes…'
      ActiveRecord::Base.connection.add_index :unavailable_domains, ['domain'], name: 'index_unavailable_domains_on_domain', unique: true
    end

    def deduplicate_email_domain_blocks!
      remove_index_if_exists!(:email_domain_blocks, 'index_email_domain_blocks_on_domain')

      @prompt.say 'Deduplicating email_domain_blocks…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM email_domain_blocks GROUP BY domain HAVING count(*) > 1").each do |row|
        domain_blocks = EmailDomainBlock.where(id: row['ids'].split(',')).sort_by { |b| b.parent.nil? ? 1 : 0 }.to_a
        domain_blocks.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring email_domain_blocks indexes…'
      ActiveRecord::Base.connection.add_index :email_domain_blocks, ['domain'], name: 'index_email_domain_blocks_on_domain', unique: true
    end

    def deduplicate_media_attachments!
      remove_index_if_exists!(:media_attachments, 'index_media_attachments_on_shortcode')

      @prompt.say 'Deduplicating media_attachments…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM media_attachments WHERE shortcode IS NOT NULL GROUP BY shortcode HAVING count(*) > 1").each do |row|
        MediaAttachment.where(id: row['ids'].split(',').drop(1)).update_all(shortcode: nil)
      end

      @prompt.say 'Restoring media_attachments indexes…'
      if ActiveRecord::Migrator.current_version < 2022_03_10_060626
        ActiveRecord::Base.connection.add_index :media_attachments, ['shortcode'], name: 'index_media_attachments_on_shortcode', unique: true
      else
        ActiveRecord::Base.connection.add_index :media_attachments, ['shortcode'], name: 'index_media_attachments_on_shortcode', unique: true, where: 'shortcode IS NOT NULL', opclass: :text_pattern_ops
      end
    end

    def deduplicate_preview_cards!
      remove_index_if_exists!(:preview_cards, 'index_preview_cards_on_url')

      @prompt.say 'Deduplicating preview_cards…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM preview_cards GROUP BY url HAVING count(*) > 1").each do |row|
        PreviewCard.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring preview_cards indexes…'
      ActiveRecord::Base.connection.add_index :preview_cards, ['url'], name: 'index_preview_cards_on_url', unique: true
    end

    def deduplicate_statuses!
      remove_index_if_exists!(:statuses, 'index_statuses_on_uri')

      @prompt.say 'Deduplicating statuses…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM statuses WHERE uri IS NOT NULL GROUP BY uri HAVING count(*) > 1").each do |row|
        statuses = Status.where(id: row['ids'].split(',')).sort_by(&:id)
        ref_status = statuses.shift
        statuses.each do |status|
          merge_statuses!(ref_status, status) if status.account_id == ref_status.account_id
          status.destroy
        end
      end

      @prompt.say 'Restoring statuses indexes…'
      if ActiveRecord::Migrator.current_version < 2022_03_10_060706
        ActiveRecord::Base.connection.add_index :statuses, ['uri'], name: 'index_statuses_on_uri', unique: true
      else
        ActiveRecord::Base.connection.add_index :statuses, ['uri'], name: 'index_statuses_on_uri', unique: true, where: 'uri IS NOT NULL', opclass: :text_pattern_ops
      end
    end

    def deduplicate_tags!
      remove_index_if_exists!(:tags, 'index_tags_on_name_lower')
      remove_index_if_exists!(:tags, 'index_tags_on_name_lower_btree')

      @prompt.say 'Deduplicating tags…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM tags GROUP BY lower((name)::text) HAVING count(*) > 1").each do |row|
        tags = Tag.where(id: row['ids'].split(',')).sort_by { |t| [t.usable?, t.trendable?, t.listable?].count(false) }
        ref_tag = tags.shift
        tags.each do |tag|
          merge_tags!(ref_tag, tag)
          tag.destroy
        end
      end

      @prompt.say 'Restoring tags indexes…'
      if ActiveRecord::Migrator.current_version < 2021_04_21_121431
        ActiveRecord::Base.connection.add_index :tags, 'lower((name)::text)', name: 'index_tags_on_name_lower', unique: true
      else
        ActiveRecord::Base.connection.execute 'CREATE UNIQUE INDEX CONCURRENTLY index_tags_on_name_lower_btree ON tags (lower(name) text_pattern_ops)'
      end
    end

    def deduplicate_webauthn_credentials!
      return unless ActiveRecord::Base.connection.table_exists?(:webauthn_credentials)

      remove_index_if_exists!(:webauthn_credentials, 'index_webauthn_credentials_on_external_id')

      @prompt.say 'Deduplicating webauthn_credentials…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM webauthn_credentials GROUP BY external_id HAVING count(*) > 1").each do |row|
        WebauthnCredential.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring webauthn_credentials indexes…'
      ActiveRecord::Base.connection.add_index :webauthn_credentials, ['external_id'], name: 'index_webauthn_credentials_on_external_id', unique: true
    end

    def deduplicate_webhooks!
      return unless ActiveRecord::Base.connection.table_exists?(:webhooks)

      remove_index_if_exists!(:webhooks, 'index_webhooks_on_url')

      @prompt.say 'Deduplicating webhooks…'
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM webhooks GROUP BY url HAVING count(*) > 1").each do |row|
        Webhooks.where(id: row['ids'].split(',')).sort_by(&:id).reverse.drop(1).each(&:destroy)
      end

      @prompt.say 'Restoring webhooks indexes…'
      ActiveRecord::Base.connection.add_index :webhooks, ['url'], name: 'index_webhooks_on_url', unique: true
    end

    def deduplicate_local_accounts!(accounts)
      accounts = accounts.sort_by(&:id).reverse

      @prompt.warn "Multiple local accounts were found for username '#{accounts.first.username}'."
      @prompt.warn 'All those accounts are distinct accounts but only the most recently-created one is fully-functional.'

      accounts.each_with_index do |account, idx|
        @prompt.say format('%2d. %s: created at: %s; updated at: %s; last logged in at: %s; statuses: %5d; last status at: %s', idx, account.username, account.created_at, account.updated_at, account.user&.last_sign_in_at&.to_s || 'N/A', account.account_stat&.statuses_count || 0, account.account_stat&.last_status_at || 'N/A')
      end

      @prompt.say 'Please chose the one to keep unchanged, other ones will be automatically renamed.'

      ref_id = @prompt.ask('Account to keep unchanged:') do |q|
        q.required true
        q.default 0
        q.convert :int
      end

      accounts.delete_at(ref_id)

      i = 0
      accounts.each do |account|
        i += 1
        username = account.username + "_#{i}"

        while Account.local.exists?(username: username)
          i += 1
          username = account.username + "_#{i}"
        end

        account.update!(username: username)
      end
    end

    def deduplicate_remote_accounts!(accounts)
      accounts = accounts.sort_by(&:updated_at).reverse

      reference_account = accounts.shift

      accounts.each do |other_account|
        if other_account.public_key == reference_account.public_key
          # The accounts definitely point to the same resource, so
          # it's safe to re-attribute content and relationships
          reference_account.merge_with!(other_account)
        end

        other_account.destroy
      end
    end

    def merge_conversations!(main_conv, duplicate_conv)
      owned_classes = [ConversationMute, AccountConversation]
      owned_classes.each do |klass|
        klass.where(conversation_id: duplicate_conv.id).find_each do |record|
          record.update_attribute(:account_id, main_conv.id)
        rescue ActiveRecord::RecordNotUnique
          next
        end
      end
    end

    def merge_custom_emojis!(main_emoji, duplicate_emoji)
      owned_classes = [AnnouncementReaction]
      owned_classes.each do |klass|
        klass.where(custom_emoji_id: duplicate_emoji.id).update_all(custom_emoji_id: main_emoji.id)
      end
    end

    def merge_custom_emoji_categories!(main_category, duplicate_category)
      owned_classes = [CustomEmoji]
      owned_classes.each do |klass|
        klass.where(category_id: duplicate_category.id).update_all(category_id: main_category.id)
      end
    end

    def merge_statuses!(main_status, duplicate_status)
      owned_classes = [Favourite, Mention, Poll]
      owned_classes << Bookmark if ActiveRecord::Base.connection.table_exists?(:bookmarks)
      owned_classes.each do |klass|
        klass.where(status_id: duplicate_status.id).find_each do |record|
          record.update_attribute(:status_id, main_status.id)
        rescue ActiveRecord::RecordNotUnique
          next
        end
      end

      StatusPin.where(account_id: main_status.account_id, status_id: duplicate_status.id).find_each do |record|
        record.update_attribute(:status_id, main_status.id)
      rescue ActiveRecord::RecordNotUnique
        next
      end

      Status.where(in_reply_to_id: duplicate_status.id).find_each do |record|
        record.update_attribute(:in_reply_to_id, main_status.id)
      rescue ActiveRecord::RecordNotUnique
        next
      end

      Status.where(reblog_of_id: duplicate_status.id).find_each do |record|
        record.update_attribute(:reblog_of_id, main_status.id)
      rescue ActiveRecord::RecordNotUnique
        next
      end
    end

    def merge_tags!(main_tag, duplicate_tag)
      [FeaturedTag].each do |klass|
        klass.where(tag_id: duplicate_tag.id).find_each do |record|
          record.update_attribute(:tag_id, main_tag.id)
        rescue ActiveRecord::RecordNotUnique
          next
        end
      end
    end

    def find_duplicate_accounts
      ActiveRecord::Base.connection.select_all("SELECT string_agg(id::text, ',') AS ids FROM accounts GROUP BY lower(username), COALESCE(lower(domain), '') HAVING count(*) > 1")
    end

    def remove_index_if_exists!(table, name)
      ActiveRecord::Base.connection.remove_index(table, name: name)
    rescue ArgumentError
      nil
    rescue ActiveRecord::StatementInvalid
      nil
    end
  end
end