content: {-# LANGUAGE QuasiQuotes #-}
  
  -- This file is part of the Wire Server implementation.
  --
  -- Copyright (C) 2022 Wire Swiss GmbH <opensource@wire.com>
  --
  -- This program is free software: you can redistribute it and/or modify it under
  -- the terms of the GNU Affero General Public License as published by the Free
  -- Software Foundation, either version 3 of the License, or (at your option) any
  -- later version.
  --
  -- This program is distributed in the hope that it will be useful, but WITHOUT
  -- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  -- FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
  -- details.
  --
  -- You should have received a copy of the GNU Affero General Public License along
  -- with this program. If not, see <https://www.gnu.org/licenses/>.
  
  module Brig.Schema.V85_DropUserKeysHashed
    ( migration,
    )
  where
  
  import Cassandra.Schema
  import Imports
  import Text.RawString.QQ
  
  -- user_keys_hash usage was removed in https://github.com/wireapp/wire-server/pull/2902
  --
  -- However, it's dangerous to remove a cassandra table together with the usage, as
  -- during deployment, there is a time window where the schema migration has run, but the
  -- old code still serves traffic, which then leads to 5xxs and user-observable errors.
  -- Therefore the policy is to wait a reasonable amount of time (6 months) to allow all
  -- installations to upgrade before removing the database tables. See also
  -- backwards-incompatbile schema migration docs in
  -- https://docs.wire.com/developer/developer/cassandra-interaction.html?highlight=backwards+incompatbile#backwards-incompatible-schema-changes
  --
  
  migration :: Migration
  migration = Migration 85 "Drop deprecated user_keys_hashed table" $ do
    schema'
      [r|
        DROP TABLE IF EXISTS user_keys_hash
     |]
  