我运行了impala查询的“explain”，得到了以下结果。我试图理解：执行命令是自下而上的吗？如果不是执行顺序，那么数字是什么意思？谢谢！

Estimated Per-Host Requirements: Memory=2.08GB VCores=2
    WARNING: The following tables are missing relevant table and/or column statistics.
    my_db.v1, my_db.v2

    10:EXCHANGE [UNPARTITIONED]
    |
    06:ANALYTIC
    |  functions: last_value(my_v_id), last_value(my__arrival_ts), last_value(version)
    |  partition by: id, trunc(my__arrival_ts, 'D')
    |  order by: my__arrival_ts ASC
    |  window: RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    |
    05:SORT
    |  order by: id ASC NULLS FIRST, trunc(my__arrival_ts, 'D') ASC NULLS FIRST, my__arrival_ts ASC
    |
    09:EXCHANGE [HASH(id,trunc(my__arrival_ts, 'D'))]
    |
    04:ANALYTIC
    |  functions: last_value(build)
    |  partition by: version
    |  order by: my__arrival_day ASC
    |  window: RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    |
    03:SORT
    |  order by: version ASC NULLS FIRST, my__arrival_day ASC
    |
    08:EXCHANGE [HASH(version)]
    |
    02:HASH JOIN [INNER JOIN, BROADCAST]
    |  hash predicates: v1__fk = v1.id
    |  runtime filters: RF000 <- v1.id
    |
    |--07:EXCHANGE [BROADCAST]
    |  |
    |  00:SCAN HDFS [my_db.v1]
    |     partitions=1791/2994 files=1956 size=125.30MB
    |     predicates: my__is_external
    |
    01:SCAN HDFS [my_db.vm]
       partitions=2058/2058 files=2094 size=9.98GB
       runtime filters: RF000 -> v1__fk