require "./check"

module Scope
  @[Meta(name: "Blocking Queries", desc: "Queries holding locks that other queries are waiting on")]
  class Blocking < Check
    def query
      <<-SQL
        SELECT bl.pid AS "blocked pid",
          ka.query               AS "blocking statement",
          now() - ka.query_start AS "blocking duration",
          kl.pid                 AS "blocking pid",
          a.query                AS "blocked statement",
          now() - a.query_start  AS "blocked duration"
        FROM pg_catalog.pg_locks bl
        JOIN pg_catalog.pg_stat_activity a
          ON bl.pid = a.pid
        JOIN pg_catalog.pg_locks kl
          JOIN pg_catalog.pg_stat_activity ka
            ON kl.pid = ka.pid
        ON bl.transactionid = kl.transactionid AND bl.pid != kl.pid
        WHERE NOT bl.granted
      SQL
    end
  end
end

# SQL modified from https://github.com/heroku/heroku-pg-extras/releases/tag/v1.2.3
#
# The MIT License (MIT)
#
# Copyright Â© Heroku 2008 - 2014
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
