DROP QUERY EXECUTOR POOL pool_name [IF bool_expr]
Drops named query executor pool.
HConnection conn = HConnectionManager.newConnection();
conn.execute("DROP QUERY EXECUTOR POOL execPool IF queryExecutorPoolExists('execPool')");
// Or, using the API
if (QueryExecutorPoolManager.queryExecutorPoolExists("execPool"))
QueryExecutorPoolManager.dropQueryExecutorPool("execPool");