KILL

KILL QUERY [ON CLUSTER cluster]
  WHERE <where expression to SELECT FROM system.processes query>
  [SYNC|ASYNC|TEST]
  [FORMAT format]

SELECT
  initial_query_id,
  query_id,
  formatReadableTimeDelta(elapsed) AS time_delta,
  query,
  *
  FROM system.processes
  WHERE query ILIKE 'SELECT%'
  ORDER BY time_delta DESC;

SELECT
  initial_query_id,
  query_id,
  formatReadableTimeDelta(elapsed) AS time_delta,
  query,
  *
  FROM clusterAllReplicas(default, system.processes)
  WHERE query ILIKE 'SELECT%'
  ORDER BY time_delta DESC;

-- Forcibly terminates all queries with the specified query_id:
KILL QUERY WHERE query_id='2-857d-4a57-9ee0-327da5d60a90'

-- Synchronously terminates all queries run by 'username':
KILL QUERY WHERE user='username' SYNC

KILL MUTATION
  WHERE <where expression to SELECT FROM system.mutations query>
  [TEST]
  [FORMAT format]

SELECT count(*)
FROM system.mutations
WHERE is_done = 0;

SELECT count(*)
FROM clusterAllReplicas('default', system.mutations)
WHERE is_done = 0;

SELECT mutation_id, *
FROM system.mutations
WHERE is_done = 0;

SELECT mutation_id, *
FROM clusterAllReplicas('default', system.mutations)
WHERE is_done = 0;

-- Cancel and remove all mutations of the single table:
KILL MUTATION WHERE database = 'default' AND table = 'table'

-- Cancel the specific mutation:
KILL MUTATION WHERE database = 'default' AND table = 'table' AND mutation_id = 'mutation_3.txt'