Resolve 01572_kill_window_function flakiness

tests/queries/0_stateless/01572_kill_window_function.sh

@@ -6,21 +6,20 @@ CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
 
 set -e -o pipefail
 
+function wait_for_query_to_start()
+{
+    while [[ $($CLICKHOUSE_CURL -sS "$CLICKHOUSE_URL" -d "SELECT count() FROM system.processes WHERE query_id = '$1'") == 0 ]]; do sleep 0.1; done
+}
+
 # Run a test query that takes very long to run.
 query_id="01572_kill_window_function-$CLICKHOUSE_DATABASE"
-$CLICKHOUSE_CLIENT --query_id="$query_id" --query "SELECT count(1048575) OVER (PARTITION BY intDiv(NULL, number) ORDER BY number DESC NULLS FIRST ROWS BETWEEN CURRENT ROW AND 1048575 FOLLOWING) FROM numbers(255, 1048575)" >/dev/null 2>&1 &
+$CLICKHOUSE_CLIENT --query_id="$query_id" --query "SELECT sum(number) OVER (PARTITION BY number % 10 ORDER BY number DESC NULLS FIRST ROWS BETWEEN CURRENT ROW AND 99999 FOLLOWING) FROM numbers(0, 10000000) format Null;" >/dev/null 2>&1 &
 client_pid=$!
 echo Started
 
-# Use one query to both kill the test query and verify that it has started,
-# because if we try to kill it before it starts, the test will fail.
-while [ -z "$($CLICKHOUSE_CLIENT --query "kill query where query_id = '$query_id' and current_database = currentDatabase()")" ]
-do
-    # If we don't yet see the query in the process list, the client should still
-    # be running. The query is very long.
-    kill -0 -- $client_pid
-    sleep 1
-done
+wait_for_query_to_start $query_id
+
+$CLICKHOUSE_CLIENT --query "kill query where query_id = '$query_id' and current_database = currentDatabase() format Null"
 echo Sent kill request
 
 # Wait for the client to terminate.