Hive调优：让任务并行执行（hive.exec.parallel）

业务背景

extract_trfc_page_kpi的hive sql如下：

set mapred.job.queue.name=pms;
set hive.exec.reducers.max=8;
set mapred.reduce.tasks=8;
set mapred.job.name=extract_trfc_page_kpi;

insert overwrite table pms.extract_trfc_page_kpi partition(ds='$yesterday')
select distinct 
    page_type_id,
    pv,
    uv,
    '$yesterday' update_time 
from
(
    --针对PC、H5
    select 
        page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi 
    where ds = '$yesterday' and stat_type = 1 
    group by page_type_id 

union all

    --PC搜索页特殊处理
    select 
        5 as page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi 
    where ds = '$yesterday' and stat_type = 1 and page_type_id in (51, 52)

union all

    --针对APP
    select 
        a.page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi a 
    left outer join (
        select distinct 
            page_type_id, 
            old_page_type_id 
        from tandem.mobile_backend_page_url_rule 
        where is_delete = 0
    ) b on (a.page_type_id = b.old_page_type_id)
    where a.ds = '$yesterday' and stat_type = 1 
    group by a.page_type_id 
) t;
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上面的sql中存在两个union all操作，顺序执行下来的话，需要耗时20分钟。

优化策略

分析以上的sql，其中union all前后的三个查询操作并无直接关联，因此没有必要顺序执行，因此优化的思路是让这三个查询操作并行执行，hive提供了如下参数实现job的并行操作：

// 开启任务并行执行
set hive.exec.parallel=true;
// 同一个sql允许并行任务的最大线程数
set hive.exec.parallel.thread.number=8;
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方案一

在执行sql时加上上面的两个hive参数，如：

set mapred.job.queue.name=pms;
set hive.exec.reducers.max=8;
set mapred.reduce.tasks=8;
set hive.exec.parallel=true;
set hive.exec.parallel.thread.number=8;
set mapred.job.name=extract_trfc_page_kpi;

insert overwrite table pms.extract_trfc_page_kpi partition(ds='$yesterday')
select distinct 
    page_type_id,
    pv,
    uv,
    '$yesterday' update_time 
from
(
    --针对PC、H5
    select 
        page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi 
    where ds = '$yesterday' and stat_type = 1 
    group by page_type_id 

union all

    --PC搜索页特殊处理
    select 
        5 as page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi 
    where ds = '$yesterday' and stat_type = 1 and page_type_id in (51, 52)

union all

    --针对APP
    select 
        a.page_type_id,
        sum(pv) as pv,
        sum(uv) as uv 
    from dw.rpt_trfc_page_kpi a 
    left outer join (
        select distinct 
            page_type_id, 
            old_page_type_id 
        from tandem.mobile_backend_page_url_rule 
        where is_delete = 0
    ) b on (a.page_type_id = b.old_page_type_id)
    where a.ds = '$yesterday' and stat_type = 1 
    group by a.page_type_id 
) t;
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方案二

在hive-site.xml中进行设置，查看当前版本hive的配置参数：

hive> set -v;
...
hive.exec.orc.zerocopy=false
hive.exec.parallel=false
hive.exec.parallel.thread.number=8
hive.exec.perf.logger=org.apache.hadoop.hive.ql.log.PerfLogger
hive.exec.rcfile.use.explicit.header=true
hive.exec.rcfile.use.sync.cache=true
hive.exec.reducers.bytes.per.reducer=1000000000
hive.exec.reducers.max=999
hive.exec.rowoffset=false
hive.exec.scratchdir=/tmp/hive-pms
hive.exec.script.allow.partial.consumption=false
hive.exec.script.maxerrsize=100000
hive.exec.script.trust=false
hive.exec.show.job.failure.debug.info=true
...
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这些参数是配置在$HIVE_HOME/conf/hive-site.xml中的，现在在这个配置文件中加入：

<property>
    <name>hive.exec.parallel</name>
    <value>true</value>
</property>
<property>
    <name>hive.exec.parallel.thread.number</name>
    <value>16</value>
</property>
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重新启动hive，看到刚刚配置的参数已经生效了：

hive> set -v;
...
hive.exec.orc.skip.corrupt.data=false
hive.exec.orc.zerocopy=false
hive.exec.parallel=true
hive.exec.parallel.thread.number=16
hive.exec.perf.logger=org.apache.hadoop.hive.ql.log.PerfLogger
hive.exec.rcfile.use.explicit.header=true
hive.exec.rcfile.use.sync.cache=true
hive.exec.reducers.bytes.per.reducer=1000000000
hive.exec.reducers.max=999
hive.exec.rowoffset=false
hive.exec.scratchdir=/tmp/hive-pms
hive.exec.script.allow.partial.consumption=false
...
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结论
经过测试，添加了这两个参数以后，extract_trfc_page_kpi脚本执行时间从耗时20分钟，优化为耗时3分钟。
接！