Hive 查看执行计划

1、基本语法

EXPLAIN [EXTENDED | DEPENDENCY | AUTHORIZATION] query-sql

执行计划关键信息

2、简单示例

2.1、先来看一个简单的栗子

explain select * from temp_shop_info;

执行计划

STAGE DEPENDENCIES:
  Stage-0 is a root stage  //这里只有一个 stage
""
STAGE PLANS:   //执行计划
  Stage: Stage-0  //Stage-0  Stage 的编号
    Fetch Operator
      limit: -1
      Processor Tree:
        TableScan  //扫描表
          alias: temp_shop_info  // 别名 这里没有给表起别名 默认是表名
          Select Operator  //查询的字段以及类型
            expressions: shop_id (type: string), commodity_id (type: string), sale (type: int)
            outputColumnNames: _col0, _col1, _col2 //输出的字段
            ListSink

2.2、下面是一个带聚合函数的执行计划

explain
select shop_id, sum(sale) sale_sum
from temp_shop_info
group by shop_id;

 执行计划 

/**
  有两个 stage ，其中 Stage-1 是根 stage，Stage-0 依赖于 Stage-1；
 */
STAGE DEPENDENCIES:
  Stage-1 is a root stage
  Stage-0 depends on stages: Stage-1

STAGE PLANS:
  Stage-1
  Stage: Stage-1
    Spark
      Edges:
        Reducer 2 <- Map 1 (GROUP, 2)
      DagName: hui_20221020203721_fefd07c4-9120-4d3f-ad13-abee4b852834:2
      Vertices:
        // map 操作
        Map 1
            Map Operator Tree:
                // 扫描表读取数据
                TableScan
                  alias: temp_shop_info
                  //表里数据的函数和大小 13 行 和 104 bt
                  Statistics: Num rows: 13 Data size: 104 Basic stats: COMPLETE Column stats: NONE
                  Select Operator //查询操作
                    expressions: shop_id (type: string), sale (type: int)
                    outputColumnNames: shop_id, sale
                    Statistics: Num rows: 13 Data size: 104 Basic stats: COMPLETE Column stats: NONE
                    Group By Operator // group
                      aggregations: sum(sale)
                      keys: shop_id (type: string)
                      mode: hash
                      outputColumnNames: _col0, _col1
                      Statistics: Num rows: 13 Data size: 104 Basic stats: COMPLETE Column stats: NONE
                      Reduce Output Operator // reduce
                        key expressions: _col0 (type: string)
                        sort order: +
                        Map-reduce partition columns: _col0 (type: string)
                        Statistics: Num rows: 13 Data size: 104 Basic stats: COMPLETE Column stats: NONE
                        value expressions: _col1 (type: bigint)
            Execution mode: vectorized
        Reducer 2 //reduce
            Execution mode: vectorized
            Reduce Operator Tree:
              Group By Operator
                aggregations: sum(VALUE._col0)
                keys: KEY._col0 (type: string)
                mode: mergepartial
                outputColumnNames: _col0, _col1
                Statistics: Num rows: 6 Data size: 48 Basic stats: COMPLETE Column stats: NONE
                File Output Operator
                  compressed: false
                  Statistics: Num rows: 6 Data size: 48 Basic stats: COMPLETE Column stats: NONE
                  table:
                      input format: org.apache.hadoop.mapred.SequenceFileInputFormat
                      output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat
                      serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
""
  Stage: Stage-0
    Fetch Operator
      limit: -1
      Processor Tree:
        ListSink
""