大数据开发之Hive优化篇4-Hive的数据抽样-Sampling

你的名字 2023-01-09 15:45 248阅读 0赞

备注:  
Hive 版本 2.1.1

### 文章目录 ###

*  抽样概述
 *  一.随机抽样
 *  二.桶表抽样
 *  三.数据块抽样
 *  参考

# 抽样概述 #

当数据量特别大时，对全体数据进行处理存在困难时，抽样就显得尤其重要了。抽样可以从被抽取的数据中估计和推断出整体的特性，是科学实验、质量检验、社会调查普遍采用的一种经济有效的工作和研究方法。

Hive中，数据抽样分为以下三种：

1.  随机抽样
2.  桶表抽样
3.  块抽样

# 一.随机抽样 #

Hive有个随机函数rand(),我们可以通过rand()函数对表进行抽样，然后用limit子句进行限制抽样数据的返回。  
其中rand函数前的distribute和sort关键字可以保证数据在mapper和reducer阶段是随机分布的。

代码:

select * from ods_fact_sale order by rand() limit 20;
    select * from ods_fact_sale where sale_date = '2011-08-16 00:00:00.0'  distribute by rand() sort by rand() limit 10;

**测试记录:**  
从测试记录可以看出，随机抽样因为需要排序，所以性能也不佳，当然会比全量数据查询性能更优一些

hive> 
        > select * from ods_fact_sale order by rand() limit 20;
    Query ID = root_20201231105936_75f9fb76-9149-4884-8faf-4254fd1e3b30
    Total jobs = 1
    Launching Job 1 out of 1
    Number of reduce tasks determined at compile time: 1
    In order to change the average load for a reducer (in bytes):
      set hive.exec.reducers.bytes.per.reducer=<number>
    In order to limit the maximum number of reducers:
      set hive.exec.reducers.max=<number>
    In order to set a constant number of reducers:
      set mapreduce.job.reduces=<number>
    20/12/31 10:59:37 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0022, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0022/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0022
    Hadoop job information for Stage-1: number of mappers: 117; number of reducers: 1
    2020-12-31 10:59:46,944 Stage-1 map = 0%,  reduce = 0%
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    MapReduce Total cumulative CPU time: 23 minutes 12 seconds 760 msec
    Ended Job = job_1609141291605_0022
    MapReduce Jobs Launched: 
    Stage-Stage-1: Map: 117  Reduce: 1   Cumulative CPU: 1392.76 sec   HDFS Read: 31436905540 HDFS Write: 1147 HDFS EC Read: 0 SUCCESS
    Total MapReduce CPU Time Spent: 23 minutes 12 seconds 760 msec
    OK
    654691105       2011-05-25 00:00:00.0   PROD10  53
    752859493       2011-11-08 00:00:00.0   PROD4   92
    620442730       2010-06-11 00:00:00.0   PROD5   22
    524983813       2011-04-11 00:00:00.0   PROD6   31
    89887602        2010-08-18 00:00:00.0   PROD7   45
    93701058        2011-10-31 00:00:00.0   PROD4   62
    739459682       2011-01-15 00:00:00.0   PROD4   93
    480818608       2010-07-12 00:00:00.0   PROD2   87
    457915153       2011-09-09 00:00:00.0   PROD9   85
    405422684       2011-11-23 00:00:00.0   PROD10  86
    322983965       2012-04-06 00:00:00.0   PROD8   7
    588940412       2010-08-15 00:00:00.0   PROD8   51
    421954935       2012-01-24 00:00:00.0   PROD4   17
    749374812       2010-12-12 00:00:00.0   PROD4   62
    298315594       2010-06-13 00:00:00.0   PROD5   75
    723116860       2011-01-17 00:00:00.0   PROD10  89
    167011022       2011-01-20 00:00:00.0   PROD4   69
    430667509       2011-07-07 00:00:00.0   PROD6   63
    665176804       2012-08-25 00:00:00.0   PROD7   77
    648219864       2012-05-15 00:00:00.0   PROD7   74
    Time taken: 814.055 seconds, Fetched: 20 row(s)
    
    hive> 
        > select * from ods_fact_sale where sale_date = '2011-08-16 00:00:00.0'  distribute by rand() sort by rand() limit 10;
    Query ID = root_20201231135813_71f7d916-8e6f-4c7a-846f-49b78194da8d
    Total jobs = 2
    Launching Job 1 out of 2
    Number of reduce tasks not specified. Estimated from input data size: 469
    In order to change the average load for a reducer (in bytes):
      set hive.exec.reducers.bytes.per.reducer=<number>
    In order to limit the maximum number of reducers:
      set hive.exec.reducers.max=<number>
    In order to set a constant number of reducers:
      set mapreduce.job.reduces=<number>
    20/12/31 13:58:14 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0023, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0023/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0023
    Hadoop job information for Stage-1: number of mappers: 117; number of reducers: 469
    2020-12-31 13:58:21,609 Stage-1 map = 0%,  reduce = 0%
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    2020-12-31 14:23:05,030 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 2016.56 sec
    MapReduce Total cumulative CPU time: 33 minutes 36 seconds 560 msec
    Ended Job = job_1609141291605_0023
    Launching Job 2 out of 2
    Number of reduce tasks determined at compile time: 1
    In order to change the average load for a reducer (in bytes):
      set hive.exec.reducers.bytes.per.reducer=<number>
    In order to limit the maximum number of reducers:
      set hive.exec.reducers.max=<number>
    In order to set a constant number of reducers:
      set mapreduce.job.reduces=<number>
    20/12/31 14:23:06 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0024, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0024/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0024
    Hadoop job information for Stage-2: number of mappers: 2; number of reducers: 1
    2020-12-31 14:23:17,212 Stage-2 map = 0%,  reduce = 0%
    2020-12-31 14:23:24,475 Stage-2 map = 50%,  reduce = 0%, Cumulative CPU 5.37 sec
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    2020-12-31 14:23:30,651 Stage-2 map = 100%,  reduce = 100%, Cumulative CPU 14.14 sec
    MapReduce Total cumulative CPU time: 14 seconds 140 msec
    Ended Job = job_1609141291605_0024
    MapReduce Jobs Launched: 
    Stage-Stage-1: Map: 117  Reduce: 469   Cumulative CPU: 2016.56 sec   HDFS Read: 31438766866 HDFS Write: 79070 HDFS EC Read: 0 SUCCESS
    Stage-Stage-2: Map: 2  Reduce: 1   Cumulative CPU: 14.14 sec   HDFS Read: 207188 HDFS Write: 614 HDFS EC Read: 0 SUCCESS
    Total MapReduce CPU Time Spent: 33 minutes 50 seconds 700 msec
    OK
    601096637       2011-08-16 00:00:00.0   PROD10  28
    7504198 2011-08-16 00:00:00.0   PROD7   22
    7666912 2011-08-16 00:00:00.0   PROD7   70
    393337914       2011-08-16 00:00:00.0   PROD5   55
    98814403        2011-08-16 00:00:00.0   PROD4   45
    744615937       2011-08-16 00:00:00.0   PROD7   73
    124859277       2011-08-16 00:00:00.0   PROD3   69
    212317100       2011-08-16 00:00:00.0   PROD10  48
    504809117       2011-08-16 00:00:00.0   PROD3   33
    268235827       2011-08-16 00:00:00.0   PROD9   91
    Time taken: 1517.782 seconds, Fetched: 10 row(s)

# 二.桶表抽样 #

Hive支持桶表抽样和块抽样。所谓桶表指的是在创建表时使用CLUSTERED BY子句创建了桶的表。桶表抽样的语法如下：

table_sample: TABLESAMPLE (BUCKET x OUT OF y [ON colname])

TABLESAMPLE子句允许用户编写用于数据抽样而不是整个表的查询，该子句出现FROM子句中，可用于任何表中。桶编号从1开始，colname表明抽取样本的列，可以是非分区列中的任意一列，或者使用rand()表明在整个行中抽取样本而不是单个列。在colname上分桶的行随机进入1到y个桶中，返回属于桶x的行。下面的例子中，返回32个桶中的第3个桶中的行：

代码:

-- 随机抽取一百分之一的数据
    select * from ods_fact_sale tablesample(bucket 1 out of 100 on rand()) limit 100

测试记录:

hive> select * from ods_fact_sale tablesample(bucket 1 out of 100 on rand()) limit 100;
    Query ID = root_20210106102309_b7fd3c38-74f3-4877-bf44-d5bb24a62a93
    Total jobs = 1
    Launching Job 1 out of 1
    Number of reduce tasks is set to 0 since there's no reduce operator
    21/01/06 10:23:11 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0029, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0029/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0029
    Hadoop job information for Stage-1: number of mappers: 117; number of reducers: 0
    2021-01-06 10:23:18,751 Stage-1 map = 0%,  reduce = 0%
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    2021-01-06 10:26:28,990 Stage-1 map = 78%,  reduce = 0%, Cumulative CPU 325.54 sec
    2021-01-06 10:26:30,010 Stage-1 map = 79%,  reduce = 0%, Cumulative CPU 328.98 sec
    2021-01-06 10:26:33,100 Stage-1 map = 80%,  reduce = 0%, Cumulative CPU 335.9 sec
    2021-01-06 10:26:36,182 Stage-1 map = 81%,  reduce = 0%, Cumulative CPU 339.46 sec
    2021-01-06 10:26:37,208 Stage-1 map = 82%,  reduce = 0%, Cumulative CPU 342.94 sec
    2021-01-06 10:26:40,278 Stage-1 map = 83%,  reduce = 0%, Cumulative CPU 346.48 sec
    2021-01-06 10:26:41,299 Stage-1 map = 84%,  reduce = 0%, Cumulative CPU 350.03 sec
    2021-01-06 10:26:44,368 Stage-1 map = 85%,  reduce = 0%, Cumulative CPU 353.74 sec
    2021-01-06 10:26:48,470 Stage-1 map = 86%,  reduce = 0%, Cumulative CPU 360.97 sec
    2021-01-06 10:26:49,519 Stage-1 map = 87%,  reduce = 0%, Cumulative CPU 364.47 sec
    2021-01-06 10:26:52,587 Stage-1 map = 88%,  reduce = 0%, Cumulative CPU 367.97 sec
    2021-01-06 10:26:53,612 Stage-1 map = 89%,  reduce = 0%, Cumulative CPU 371.48 sec
    2021-01-06 10:26:56,714 Stage-1 map = 90%,  reduce = 0%, Cumulative CPU 375.17 sec
    2021-01-06 10:26:57,740 Stage-1 map = 91%,  reduce = 0%, Cumulative CPU 378.75 sec
    2021-01-06 10:27:01,849 Stage-1 map = 92%,  reduce = 0%, Cumulative CPU 386.16 sec
    2021-01-06 10:27:04,955 Stage-1 map = 93%,  reduce = 0%, Cumulative CPU 389.82 sec
    2021-01-06 10:27:05,978 Stage-1 map = 94%,  reduce = 0%, Cumulative CPU 393.33 sec
    2021-01-06 10:27:09,048 Stage-1 map = 95%,  reduce = 0%, Cumulative CPU 397.01 sec
    2021-01-06 10:27:10,079 Stage-1 map = 96%,  reduce = 0%, Cumulative CPU 400.49 sec
    2021-01-06 10:27:13,200 Stage-1 map = 97%,  reduce = 0%, Cumulative CPU 404.31 sec
    2021-01-06 10:27:16,273 Stage-1 map = 98%,  reduce = 0%, Cumulative CPU 411.48 sec
    2021-01-06 10:27:18,312 Stage-1 map = 99%,  reduce = 0%, Cumulative CPU 414.97 sec
    2021-01-06 10:27:20,354 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 418.35 sec
    MapReduce Total cumulative CPU time: 6 minutes 58 seconds 350 msec
    Ended Job = job_1609141291605_0029
    MapReduce Jobs Launched: 
    Stage-Stage-1: Map: 117   Cumulative CPU: 418.35 sec   HDFS Read: 62555036 HDFS Write: 629015 HDFS EC Read: 0 SUCCESS
    Total MapReduce CPU Time Spent: 6 minutes 58 seconds 350 msec
    OK
    169387977       2011-01-30 00:00:00.0   PROD10  87
    169387995       2011-05-10 00:00:00.0   PROD6   86
    169388013       2011-04-14 00:00:00.0   PROD10  46
    169388092       2010-06-07 00:00:00.0   PROD3   34
    169388149       2010-06-21 00:00:00.0   PROD7   16
    169388210       2011-10-05 00:00:00.0   PROD3   85
    169388272       2012-02-27 00:00:00.0   PROD6   65
    169388359       2012-08-30 00:00:00.0   PROD10  10
    169388383       2011-11-09 00:00:00.0   PROD5   95
    169388414       2011-07-25 00:00:00.0   PROD2   35
    169388433       2011-05-18 00:00:00.0   PROD9   85
    169388697       2010-12-25 00:00:00.0   PROD9   20
    169388811       2012-04-03 00:00:00.0   PROD9   49
    169388872       2010-11-23 00:00:00.0   PROD7   71
    169388935       2012-04-18 00:00:00.0   PROD6   62
    169389026       2011-03-21 00:00:00.0   PROD10  80
    169389070       2010-09-09 00:00:00.0   PROD3   90
    169389083       2010-05-20 00:00:00.0   PROD3   41
    169389370       2011-01-28 00:00:00.0   PROD6   39
    169389409       2012-08-09 00:00:00.0   PROD2   20
    169389430       2012-08-23 00:00:00.0   PROD3   47
    169389517       2011-10-25 00:00:00.0   PROD8   33
    169389759       2010-09-03 00:00:00.0   PROD3   14
    169389802       2010-08-22 00:00:00.0   PROD3   55
    169389899       2012-01-14 00:00:00.0   PROD5   80
    169389935       2010-06-10 00:00:00.0   PROD9   25
    169390249       2010-09-05 00:00:00.0   PROD7   89
    169390332       2012-07-28 00:00:00.0   PROD9   24
    169390405       2011-09-30 00:00:00.0   PROD6   82
    169390432       2010-09-04 00:00:00.0   PROD6   3
    169390525       2011-04-24 00:00:00.0   PROD6   50
    169390529       2012-06-29 00:00:00.0   PROD4   36
    169390596       2011-09-29 00:00:00.0   PROD2   69
    169390726       2011-01-09 00:00:00.0   PROD4   20
    169390784       2011-08-20 00:00:00.0   PROD7   19
    169390821       2010-07-14 00:00:00.0   PROD4   44
    169390835       2010-09-24 00:00:00.0   PROD2   15
    169390858       2012-08-08 00:00:00.0   PROD5   3
    169391297       2011-03-24 00:00:00.0   PROD10  75
    169391461       2012-03-14 00:00:00.0   PROD4   32
    169391509       2010-11-23 00:00:00.0   PROD3   28
    169391526       2012-03-28 00:00:00.0   PROD6   35
    169391558       2011-02-21 00:00:00.0   PROD2   79
    169391632       2010-10-09 00:00:00.0   PROD9   37
    169391649       2012-09-22 00:00:00.0   PROD8   80
    169391761       2011-03-15 00:00:00.0   PROD7   45
    169391765       2011-01-23 00:00:00.0   PROD4   71
    169391951       2012-03-08 00:00:00.0   PROD3   97
    169392051       2011-05-13 00:00:00.0   PROD9   27
    169392357       2010-05-22 00:00:00.0   PROD4   8
    169392408       2011-01-06 00:00:00.0   PROD7   31
    169392481       2012-07-25 00:00:00.0   PROD10  81
    169392709       2012-08-12 00:00:00.0   PROD3   75
    169392782       2012-07-28 00:00:00.0   PROD2   8
    169392825       2011-03-14 00:00:00.0   PROD7   89
    169392843       2010-10-31 00:00:00.0   PROD3   19
    169392864       2011-05-19 00:00:00.0   PROD4   88
    169392979       2012-05-11 00:00:00.0   PROD4   65
    169393180       2011-05-02 00:00:00.0   PROD4   99
    169393214       2011-10-27 00:00:00.0   PROD7   31
    169393460       2012-07-27 00:00:00.0   PROD8   63
    169393613       2011-03-03 00:00:00.0   PROD9   55
    169393624       2010-04-24 00:00:00.0   PROD7   80
    169393740       2011-08-17 00:00:00.0   PROD8   71
    169394026       2012-06-07 00:00:00.0   PROD9   76
    169394117       2012-02-29 00:00:00.0   PROD4   72
    169394147       2011-12-23 00:00:00.0   PROD7   53
    169394177       2011-01-07 00:00:00.0   PROD7   35
    169394508       2012-05-24 00:00:00.0   PROD3   88
    169394552       2011-07-16 00:00:00.0   PROD4   41
    169394614       2010-08-17 00:00:00.0   PROD6   98
    169394631       2010-09-23 00:00:00.0   PROD10  45
    169394679       2011-01-22 00:00:00.0   PROD6   57
    169394778       2011-09-03 00:00:00.0   PROD10  45
    169394824       2011-06-04 00:00:00.0   PROD8   82
    169394827       2010-07-14 00:00:00.0   PROD9   42
    169394830       2012-03-09 00:00:00.0   PROD10  36
    169394864       2010-09-17 00:00:00.0   PROD9   56
    169394881       2011-07-01 00:00:00.0   PROD6   7
    169395019       2011-11-17 00:00:00.0   PROD6   66
    169395142       2012-01-21 00:00:00.0   PROD6   54
    169395197       2012-08-10 00:00:00.0   PROD5   72
    169395226       2010-09-20 00:00:00.0   PROD3   88
    169395253       2011-12-31 00:00:00.0   PROD4   56
    169395358       2010-07-16 00:00:00.0   PROD2   75
    169395367       2010-12-16 00:00:00.0   PROD4   86
    169395398       2012-01-07 00:00:00.0   PROD5   18
    169395418       2011-05-08 00:00:00.0   PROD7   82
    169395463       2011-08-23 00:00:00.0   PROD9   44
    169395636       2011-01-16 00:00:00.0   PROD8   11
    169395766       2012-06-05 00:00:00.0   PROD4   43
    169395909       2011-12-10 00:00:00.0   PROD5   79
    169395943       2012-05-11 00:00:00.0   PROD4   27
    169395960       2012-01-17 00:00:00.0   PROD7   43
    169396093       2011-08-28 00:00:00.0   PROD8   60
    169396142       2010-11-13 00:00:00.0   PROD7   46
    169396183       2011-06-16 00:00:00.0   PROD8   88
    169396195       2010-10-06 00:00:00.0   PROD3   60
    169396279       2012-06-18 00:00:00.0   PROD2   65
    169396328       2011-05-14 00:00:00.0   PROD5   21
    Time taken: 251.799 seconds, Fetched: 100 row(s)
    hive>

# 三.数据块抽样 #

1） tablesample(n percent) 根据hive表数据的大小按比例抽取数据，并保存到新的hive表中。如：抽取原hive表中10%的数据  
（注意：测试过程中发现，select语句不能带where条件且不支持子查询，可通过新建中间表或使用随机抽样解决）  
create table xxx\_new as select \* from xxx tablesample(10 percent)  
2）tablesample(n M) 指定抽样数据的大小，单位为M。  
3）tablesample(n rows) 指定抽样数据的行数，其中n代表每个map任务均取n行数据，map数量可通过hive表的简单查询语句确认（关键词：number of mappers: x)

代码:

create table sample_test1 as select * from ods_fact_sale tablesample(10000 rows);

测试记录:

hive> 
        > create table sample_test1 as select * from ods_fact_sale tablesample(10000 rows);
    Query ID = root_20210106103549_9aaeea0b-6414-40ea-af0b-2942c80ad3a4
    Total jobs = 3
    Launching Job 1 out of 3
    Number of reduce tasks is set to 0 since there's no reduce operator
    21/01/06 10:35:50 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0031, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0031/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0031
    Hadoop job information for Stage-1: number of mappers: 117; number of reducers: 0
    2021-01-06 10:43:18,970 Stage-1 map = 0%,  reduce = 0%
    2021-01-06 10:43:25,150 Stage-1 map = 1%,  reduce = 0%, Cumulative CPU 2.23 sec
    2021-01-06 10:43:26,183 Stage-1 map = 2%,  reduce = 0%, Cumulative CPU 4.48 sec
    2021-01-06 10:43:29,274 Stage-1 map = 3%,  reduce = 0%, Cumulative CPU 6.63 sec
    2021-01-06 10:43:33,375 Stage-1 map = 4%,  reduce = 0%, Cumulative CPU 10.81 sec
    2021-01-06 10:43:34,415 Stage-1 map = 5%,  reduce = 0%, Cumulative CPU 13.01 sec
    2021-01-06 10:43:37,513 Stage-1 map = 6%,  reduce = 0%, Cumulative CPU 15.14 sec
    2021-01-06 10:43:38,545 Stage-1 map = 7%,  reduce = 0%, Cumulative CPU 17.34 sec
    2021-01-06 10:43:41,660 Stage-1 map = 9%,  reduce = 0%, Cumulative CPU 22.66 sec
    2021-01-06 10:43:45,757 Stage-1 map = 10%,  reduce = 0%, Cumulative CPU 27.05 sec
    2021-01-06 10:43:48,836 Stage-1 map = 11%,  reduce = 0%, Cumulative CPU 29.23 sec
    2021-01-06 10:43:49,866 Stage-1 map = 12%,  reduce = 0%, Cumulative CPU 31.3 sec
    2021-01-06 10:43:53,953 Stage-1 map = 14%,  reduce = 0%, Cumulative CPU 36.41 sec
    2021-01-06 10:43:57,029 Stage-1 map = 15%,  reduce = 0%, Cumulative CPU 38.51 sec
    2021-01-06 10:44:01,131 Stage-1 map = 16%,  reduce = 0%, Cumulative CPU 42.67 sec
    2021-01-06 10:44:02,159 Stage-1 map = 17%,  reduce = 0%, Cumulative CPU 44.8 sec
    2021-01-06 10:44:05,239 Stage-1 map = 18%,  reduce = 0%, Cumulative CPU 47.68 sec
    2021-01-06 10:44:06,263 Stage-1 map = 19%,  reduce = 0%, Cumulative CPU 49.82 sec
    2021-01-06 10:44:09,337 Stage-1 map = 20%,  reduce = 0%, Cumulative CPU 51.91 sec
    2021-01-06 10:44:10,363 Stage-1 map = 21%,  reduce = 0%, Cumulative CPU 54.01 sec
    2021-01-06 10:44:14,485 Stage-1 map = 22%,  reduce = 0%, Cumulative CPU 58.3 sec
    2021-01-06 10:44:17,602 Stage-1 map = 23%,  reduce = 0%, Cumulative CPU 60.69 sec
    2021-01-06 10:44:18,629 Stage-1 map = 24%,  reduce = 0%, Cumulative CPU 62.8 sec
    2021-01-06 10:44:20,695 Stage-1 map = 25%,  reduce = 0%, Cumulative CPU 62.8 sec
    2021-01-06 10:44:21,722 Stage-1 map = 26%,  reduce = 0%, Cumulative CPU 67.1 sec
    2021-01-06 10:44:25,807 Stage-1 map = 27%,  reduce = 0%, Cumulative CPU 72.28 sec
    2021-01-06 10:44:28,901 Stage-1 map = 28%,  reduce = 0%, Cumulative CPU 74.58 sec
    2021-01-06 10:44:29,928 Stage-1 map = 29%,  reduce = 0%, Cumulative CPU 76.67 sec
    2021-01-06 10:44:33,007 Stage-1 map = 30%,  reduce = 0%, Cumulative CPU 78.79 sec
    2021-01-06 10:44:34,028 Stage-1 map = 31%,  reduce = 0%, Cumulative CPU 80.96 sec
    2021-01-06 10:44:37,102 Stage-1 map = 32%,  reduce = 0%, Cumulative CPU 83.07 sec
    2021-01-06 10:44:41,245 Stage-1 map = 33%,  reduce = 0%, Cumulative CPU 87.27 sec
    2021-01-06 10:44:42,273 Stage-1 map = 34%,  reduce = 0%, Cumulative CPU 89.43 sec
    2021-01-06 10:44:45,358 Stage-1 map = 35%,  reduce = 0%, Cumulative CPU 91.67 sec
    2021-01-06 10:44:46,384 Stage-1 map = 36%,  reduce = 0%, Cumulative CPU 93.74 sec
    2021-01-06 10:44:49,455 Stage-1 map = 37%,  reduce = 0%, Cumulative CPU 95.87 sec
    2021-01-06 10:44:50,475 Stage-1 map = 38%,  reduce = 0%, Cumulative CPU 97.96 sec
    2021-01-06 10:44:54,573 Stage-1 map = 39%,  reduce = 0%, Cumulative CPU 102.2 sec
    2021-01-06 10:44:57,641 Stage-1 map = 40%,  reduce = 0%, Cumulative CPU 104.33 sec
    2021-01-06 10:44:58,664 Stage-1 map = 41%,  reduce = 0%, Cumulative CPU 106.43 sec
    2021-01-06 10:45:01,731 Stage-1 map = 42%,  reduce = 0%, Cumulative CPU 108.6 sec
    2021-01-06 10:45:02,748 Stage-1 map = 43%,  reduce = 0%, Cumulative CPU 110.65 sec
    2021-01-06 10:45:05,815 Stage-1 map = 44%,  reduce = 0%, Cumulative CPU 112.77 sec
    2021-01-06 10:45:09,914 Stage-1 map = 45%,  reduce = 0%, Cumulative CPU 117.8 sec
    2021-01-06 10:45:11,961 Stage-1 map = 46%,  reduce = 0%, Cumulative CPU 120.7 sec
    2021-01-06 10:45:13,062 Stage-1 map = 47%,  reduce = 0%, Cumulative CPU 122.89 sec
    2021-01-06 10:45:15,114 Stage-1 map = 48%,  reduce = 0%, Cumulative CPU 125.05 sec
    2021-01-06 10:45:17,165 Stage-1 map = 49%,  reduce = 0%, Cumulative CPU 127.48 sec
    2021-01-06 10:45:19,206 Stage-1 map = 50%,  reduce = 0%, Cumulative CPU 129.7 sec
    2021-01-06 10:45:23,292 Stage-1 map = 51%,  reduce = 0%, Cumulative CPU 134.0 sec
    2021-01-06 10:45:25,332 Stage-1 map = 52%,  reduce = 0%, Cumulative CPU 136.29 sec
    2021-01-06 10:45:27,388 Stage-1 map = 53%,  reduce = 0%, Cumulative CPU 138.46 sec
    2021-01-06 10:45:29,446 Stage-1 map = 54%,  reduce = 0%, Cumulative CPU 140.55 sec
    2021-01-06 10:45:31,492 Stage-1 map = 55%,  reduce = 0%, Cumulative CPU 142.66 sec
    2021-01-06 10:45:33,543 Stage-1 map = 56%,  reduce = 0%, Cumulative CPU 144.88 sec
    2021-01-06 10:45:37,635 Stage-1 map = 57%,  reduce = 0%, Cumulative CPU 149.09 sec
    2021-01-06 10:45:39,684 Stage-1 map = 58%,  reduce = 0%, Cumulative CPU 151.19 sec
    2021-01-06 10:45:41,722 Stage-1 map = 59%,  reduce = 0%, Cumulative CPU 153.36 sec
    2021-01-06 10:45:43,772 Stage-1 map = 60%,  reduce = 0%, Cumulative CPU 155.63 sec
    2021-01-06 10:45:45,845 Stage-1 map = 61%,  reduce = 0%, Cumulative CPU 157.83 sec
    2021-01-06 10:45:47,898 Stage-1 map = 62%,  reduce = 0%, Cumulative CPU 160.0 sec
    2021-01-06 10:45:50,964 Stage-1 map = 63%,  reduce = 0%, Cumulative CPU 164.4 sec
    2021-01-06 10:45:53,011 Stage-1 map = 64%,  reduce = 0%, Cumulative CPU 166.52 sec
    2021-01-06 10:45:56,082 Stage-1 map = 65%,  reduce = 0%, Cumulative CPU 169.38 sec
    2021-01-06 10:45:57,100 Stage-1 map = 66%,  reduce = 0%, Cumulative CPU 171.54 sec
    2021-01-06 10:45:59,150 Stage-1 map = 67%,  reduce = 0%, Cumulative CPU 173.78 sec
    2021-01-06 10:46:01,196 Stage-1 map = 68%,  reduce = 0%, Cumulative CPU 175.86 sec
    2021-01-06 10:46:05,279 Stage-1 map = 69%,  reduce = 0%, Cumulative CPU 180.23 sec
    2021-01-06 10:46:07,323 Stage-1 map = 70%,  reduce = 0%, Cumulative CPU 182.35 sec
    2021-01-06 10:46:09,367 Stage-1 map = 71%,  reduce = 0%, Cumulative CPU 184.54 sec
    2021-01-06 10:46:11,417 Stage-1 map = 72%,  reduce = 0%, Cumulative CPU 186.79 sec
    2021-01-06 10:46:13,466 Stage-1 map = 73%,  reduce = 0%, Cumulative CPU 189.05 sec
    2021-01-06 10:46:15,512 Stage-1 map = 74%,  reduce = 0%, Cumulative CPU 191.37 sec
    2021-01-06 10:46:19,604 Stage-1 map = 75%,  reduce = 0%, Cumulative CPU 196.46 sec
    2021-01-06 10:46:21,656 Stage-1 map = 76%,  reduce = 0%, Cumulative CPU 198.58 sec
    2021-01-06 10:46:23,700 Stage-1 map = 77%,  reduce = 0%, Cumulative CPU 200.71 sec
    2021-01-06 10:46:25,743 Stage-1 map = 78%,  reduce = 0%, Cumulative CPU 202.83 sec
    2021-01-06 10:46:27,790 Stage-1 map = 79%,  reduce = 0%, Cumulative CPU 205.01 sec
    2021-01-06 10:46:31,884 Stage-1 map = 80%,  reduce = 0%, Cumulative CPU 210.06 sec
    2021-01-06 10:46:33,933 Stage-1 map = 81%,  reduce = 0%, Cumulative CPU 212.22 sec
    2021-01-06 10:46:36,001 Stage-1 map = 82%,  reduce = 0%, Cumulative CPU 215.35 sec
    2021-01-06 10:46:38,047 Stage-1 map = 83%,  reduce = 0%, Cumulative CPU 217.44 sec
    2021-01-06 10:46:40,097 Stage-1 map = 84%,  reduce = 0%, Cumulative CPU 219.61 sec
    2021-01-06 10:46:42,146 Stage-1 map = 85%,  reduce = 0%, Cumulative CPU 221.86 sec
    2021-01-06 10:46:45,215 Stage-1 map = 86%,  reduce = 0%, Cumulative CPU 226.88 sec
    2021-01-06 10:46:47,259 Stage-1 map = 87%,  reduce = 0%, Cumulative CPU 229.08 sec
    2021-01-06 10:46:50,350 Stage-1 map = 88%,  reduce = 0%, Cumulative CPU 231.42 sec
    2021-01-06 10:46:51,376 Stage-1 map = 89%,  reduce = 0%, Cumulative CPU 233.67 sec
    2021-01-06 10:46:53,421 Stage-1 map = 90%,  reduce = 0%, Cumulative CPU 235.9 sec
    2021-01-06 10:46:55,456 Stage-1 map = 91%,  reduce = 0%, Cumulative CPU 238.13 sec
    2021-01-06 10:46:59,543 Stage-1 map = 92%,  reduce = 0%, Cumulative CPU 242.35 sec
    2021-01-06 10:47:01,588 Stage-1 map = 93%,  reduce = 0%, Cumulative CPU 244.55 sec
    2021-01-06 10:47:03,636 Stage-1 map = 94%,  reduce = 0%, Cumulative CPU 246.69 sec
    2021-01-06 10:47:05,701 Stage-1 map = 95%,  reduce = 0%, Cumulative CPU 248.95 sec
    2021-01-06 10:47:07,755 Stage-1 map = 96%,  reduce = 0%, Cumulative CPU 251.08 sec
    2021-01-06 10:47:09,798 Stage-1 map = 97%,  reduce = 0%, Cumulative CPU 253.23 sec
    2021-01-06 10:47:13,877 Stage-1 map = 98%,  reduce = 0%, Cumulative CPU 257.48 sec
    2021-01-06 10:47:15,930 Stage-1 map = 99%,  reduce = 0%, Cumulative CPU 259.56 sec
    2021-01-06 10:47:17,973 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 262.3 sec
    MapReduce Total cumulative CPU time: 4 minutes 22 seconds 300 msec
    Ended Job = job_1609141291605_0031
    Stage-4 is filtered out by condition resolver.
    Stage-3 is selected by condition resolver.
    Stage-5 is filtered out by condition resolver.
    Launching Job 3 out of 3
    Number of reduce tasks is set to 0 since there's no reduce operator
    21/01/06 10:47:19 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0032, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0032/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0032
    Hadoop job information for Stage-3: number of mappers: 1; number of reducers: 0
    2021-01-06 10:47:29,293 Stage-3 map = 0%,  reduce = 0%
    2021-01-06 10:47:37,518 Stage-3 map = 100%,  reduce = 0%, Cumulative CPU 5.67 sec
    MapReduce Total cumulative CPU time: 5 seconds 670 msec
    Ended Job = job_1609141291605_0032
    Moving data to directory hdfs://nameservice1/user/hive/warehouse/test.db/sample_test1
    MapReduce Jobs Launched: 
    Stage-Stage-1: Map: 117   Cumulative CPU: 262.3 sec   HDFS Read: 61853025 HDFS Write: 47856547 HDFS EC Read: 0 SUCCESS
    Stage-Stage-3: Map: 1   Cumulative CPU: 5.67 sec   HDFS Read: 47866656 HDFS Write: 47847187 HDFS EC Read: 0 SUCCESS
    Total MapReduce CPU Time Spent: 4 minutes 27 seconds 970 msec
    OK
    Time taken: 709.589 seconds
    hive> 
        > select count(*) from sample_test1;
    Query ID = root_20210106105110_0c94562d-021f-45ac-bf4e-d0fa98dcf849
    Total jobs = 1
    Launching Job 1 out of 1
    Number of reduce tasks determined at compile time: 1
    In order to change the average load for a reducer (in bytes):
      set hive.exec.reducers.bytes.per.reducer=<number>
    In order to limit the maximum number of reducers:
      set hive.exec.reducers.max=<number>
    In order to set a constant number of reducers:
      set mapreduce.job.reduces=<number>
    21/01/06 10:51:10 INFO client.ConfiguredRMFailoverProxyProvider: Failing over to rm69
    Starting Job = job_1609141291605_0033, Tracking URL = http://hp3:8088/proxy/application_1609141291605_0033/
    Kill Command = /opt/cloudera/parcels/CDH-6.3.1-1.cdh6.3.1.p0.1470567/lib/hadoop/bin/hadoop job  -kill job_1609141291605_0033
    Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 1
    2021-01-06 10:51:17,757 Stage-1 map = 0%,  reduce = 0%
    2021-01-06 10:51:25,012 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 3.8 sec
    2021-01-06 10:51:30,170 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 6.23 sec
    MapReduce Total cumulative CPU time: 6 seconds 230 msec
    Ended Job = job_1609141291605_0033
    MapReduce Jobs Launched: 
    Stage-Stage-1: Map: 1  Reduce: 1   Cumulative CPU: 6.23 sec   HDFS Read: 47855329 HDFS Write: 107 HDFS EC Read: 0 SUCCESS
    Total MapReduce CPU Time Spent: 6 seconds 230 msec
    OK
    1170000
    Time taken: 20.625 seconds, Fetched: 1 row(s)
    hive>

# 参考 #

1.https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Sampling  
2.https://blog.csdn.net/baidu\_20183817/article/details/84099049