有什么方法可以提高hql的性能吗？我有这样一个问题：

with
tmp_a as (
SELECT * FROM `zhihu.answer` where ym in (select distinct(ym) from zhihu.answer_increment)
),
-- the result of subquery select distinct(ym) from zhihu.answer_increment is 201806
-- the rows of tmp_a are 1,790,000
tmp1 as (
select a.* from tmp_a a
LEFT JOIN `zhihu.answer_increment` b
ON a.answer_id = b.answer_id
AND a.insert_time = b.insert_time
WHERE b.answer_id IS NULL)

insert overwrite table zhihu.answer partition(ym)
select * from tmp1
UNION ALL
SELECT *
FROM `zhihu.answer_increment` t

表信息：

Rows of `zhihu.answer` are about 10 millions. and was partitioned by `ym`, that means year and month,
and was clustered by `answer_id` into 256 buckets.
Rows of `zhihu.answer_increment` are about 100 thousands.

the data structure of these two tables are the same.

上述查询的目的是合并新创建的数据( answer_increment table )历史数据( answer table )，并保存到Hive中。
问题是整个过程大约花了2个小时来运行，是否有任何优化上述hql？
我尝试创建表的索引，但不确定这是否有帮助：

CREATE INDEX insert_time_index ON TABLE zhihu.answer (insert_time) AS 'COMPACT'
 WITH DEFERRED REBUILD;

我的Hive设置：

set hive.auto.convert.join=true;

我的hql解释：

Explain 
STAGE DEPENDENCIES: 
  Stage-5 is a root stage   
  Stage-11 depends on stages: Stage-5 , consists of Stage-13, Stage-1   
  Stage-13 has a backup stage: Stage-1  
  Stage-10 depends on stages: Stage-13  
  Stage-9 depends on stages: Stage-1, Stage-10 , consists of Stage-12, Stage-2  
  Stage-12 has a backup stage: Stage-2  
  Stage-8 depends on stages: Stage-12   
  Stage-3 depends on stages: Stage-2, Stage-8   
  Stage-0 depends on stages: Stage-3    
  Stage-4 depends on stages: Stage-0    
  Stage-2   
  Stage-1   

STAGE PLANS:    
  Stage: Stage-5    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            alias: zhihu_answer_increment   
            filterExpr: ym is not null (type: boolean)  
            Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: COMPLETE   
            Select Operator 
              expressions: ym (type: string)    
              outputColumnNames: ym 
              Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: COMPLETE 
              Group By Operator 
                keys: ym (type: string) 
                mode: hash  
                outputColumnNames: _col0    
                Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE 
                Reduce Output Operator  
                  key expressions: _col0 (type: string) 
                  sort order: + 
                  Map-reduce partition columns: _col0 (type: string)    
                  Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE   
      Execution mode: vectorized    
      Reduce Operator Tree: 
        Group By Operator   
          keys: KEY._col0 (type: string)    
          mode: mergepartial    
          outputColumnNames: _col0  
          Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE   
          Group By Operator 
            keys: _col0 (type: string)  
            mode: hash  
            outputColumnNames: _col0    
            Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE 
            File Output Operator    
              compressed: false 
              table:    
                  input format: org.apache.hadoop.mapred.SequenceFileInputFormat    
                  output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat  
                  serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe   

  Stage: Stage-11   
    Conditional Operator    

  Stage: Stage-13   
    Map Reduce Local Work   
      Alias -> Map Local Tables:    
        _u1-subquery1:tmp1:a:$INTNAME   
          Fetch Operator    
            limit: -1   
      Alias -> Map Local Operator Tree: 
        _u1-subquery1:tmp1:a:$INTNAME   
          TableScan 
            HashTable Sink Operator 
              keys: 
                0 ym (type: string) 
                1 _col0 (type: string)  

  Stage: Stage-10   
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            alias: zhihu.zhihu_answer   
            filterExpr: ym is not null (type: boolean)  
            Statistics: Num rows: 76466394 Data size: 16134409134 Basic stats: COMPLETE Column stats: PARTIAL   
            Map Join Operator   
              condition map:    
                   Left Semi Join 0 to 1    
              keys: 
                0 ym (type: string) 
                1 _col0 (type: string)  
              outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
              Statistics: Num rows: 4024547 Data size: 7356871916 Basic stats: COMPLETE Column stats: PARTIAL   
              File Output Operator  
                compressed: false   
                table:  
                    input format: org.apache.hadoop.mapred.SequenceFileInputFormat  
                    output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat    
                    serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe 
      Local Work:   
        Map Reduce Local Work   

  Stage: Stage-9    
    Conditional Operator    

  Stage: Stage-12   
    Map Reduce Local Work   
      Alias -> Map Local Tables:    
        _u1-subquery1:tmp1:b    
          Fetch Operator    
            limit: -1   
      Alias -> Map Local Operator Tree: 
        _u1-subquery1:tmp1:b    
          TableScan 
            alias: b    
            Statistics: Num rows: 101549 Data size: 2741823 Basic stats: COMPLETE Column stats: NONE    
            HashTable Sink Operator 
              keys: 
                0 _col3 (type: string), _col15 (type: string)   
                1 answer_id (type: string), insert_time (type: string)  

  Stage: Stage-8    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            Map Join Operator   
              condition map:    
                   Left Outer Join0 to 1    
              keys: 
                0 _col3 (type: string), _col15 (type: string)   
                1 answer_id (type: string), insert_time (type: string)  
              outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27, _col31   
              Statistics: Num rows: 4427001 Data size: 8092559283 Basic stats: COMPLETE Column stats: NONE  
              Filter Operator   
                predicate: _col31 is null (type: boolean)   
                Statistics: Num rows: 2213500 Data size: 4046278727 Basic stats: COMPLETE Column stats: NONE    
                Select Operator 
                  expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col3 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col13 (type: int), _col14 (type: string), _col15 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string) 
                  outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
                  Statistics: Num rows: 2213500 Data size: 4046278727 Basic stats: COMPLETE Column stats: NONE  
                  File Output Operator  
                    compressed: false   
                    table:  
                        input format: org.apache.hadoop.mapred.SequenceFileInputFormat  
                        output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat    
                        serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe 
      Local Work:   
        Map Reduce Local Work   

  Stage: Stage-3    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            Union   
              Statistics: Num rows: 2315049 Data size: 4067705566 Basic stats: COMPLETE Column stats: PARTIAL   
              Reduce Output Operator    
                sort order:     
                Map-reduce partition columns: _col3 (type: string)  
                Statistics: Num rows: 2315049 Data size: 4067705566 Basic stats: COMPLETE Column stats: PARTIAL 
                value expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col3 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col13 (type: int), _col14 (type: string), _col15 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string) 
          TableScan 
            alias: t    
            Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: PARTIAL    
            Select Operator 
              expressions: admin_closed_comment (type: boolean), answer_content (type: string), answer_created (type: string), answer_id (type: string), answer_updated (type: string), author_headline (type: string), author_id (type: string), author_name (type: string), author_type (type: string), author_url_token (type: string), avatar_url (type: string), badge_num (type: smallint), can_comment (type: boolean), comment_count (type: int), gender (type: string), insert_time (type: string), is_advertiser (type: boolean), is_collapsed (type: boolean), is_copyable (type: boolean), is_org (type: boolean), question_created (type: string), question_id (type: string), question_title (type: string), question_type (type: string), reward_member_count (type: int), reward_total_money (type: int), voteup_count (type: int), ym (type: string)   
              outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
              Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: PARTIAL  
              Union 
                Statistics: Num rows: 2315049 Data size: 4067705566 Basic stats: COMPLETE Column stats: PARTIAL 
                Reduce Output Operator  
                  sort order:   
                  Map-reduce partition columns: _col3 (type: string)    
                  Statistics: Num rows: 2315049 Data size: 4067705566 Basic stats: COMPLETE Column stats: PARTIAL   
                  value expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col3 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col13 (type: int), _col14 (type: string), _col15 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string)   
      Reduce Operator Tree: 
        Select Operator 
          expressions: VALUE._col0 (type: boolean), VALUE._col1 (type: string), VALUE._col2 (type: string), VALUE._col3 (type: string), VALUE._col4 (type: string), VALUE._col5 (type: string), VALUE._col6 (type: string), VALUE._col7 (type: string), VALUE._col8 (type: string), VALUE._col9 (type: string), VALUE._col10 (type: string), VALUE._col11 (type: smallint), VALUE._col12 (type: boolean), VALUE._col13 (type: int), VALUE._col14 (type: string), VALUE._col15 (type: string), VALUE._col16 (type: boolean), VALUE._col17 (type: boolean), VALUE._col18 (type: boolean), VALUE._col19 (type: boolean), VALUE._col20 (type: string), VALUE._col21 (type: string), VALUE._col22 (type: string), VALUE._col23 (type: string), VALUE._col24 (type: int), VALUE._col25 (type: int), VALUE._col26 (type: int), VALUE._col27 (type: string) 
          outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
          Statistics: Num rows: 2315049 Data size: 425969016 Basic stats: COMPLETE Column stats: PARTIAL    
          File Output Operator  
            compressed: false   
            Statistics: Num rows: 2315049 Data size: 425969016 Basic stats: COMPLETE Column stats: PARTIAL  
            table:  
                input format: org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat 
                output format: org.apache.hadoop.hive.ql.io.parquet.MapredParquetOutputFormat   
                serde: org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe  
                name: zhihu.zhihu_answer    

  Stage: Stage-0    
    Move Operator   
      tables:   
          partition:    
            ym  
          replace: true 
          table:    
              input format: org.apache.hadoop.hive.ql.io.parquet.MapredParquetInputFormat   
              output format: org.apache.hadoop.hive.ql.io.parquet.MapredParquetOutputFormat 
              serde: org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe    
              name: zhihu.zhihu_answer  

  Stage: Stage-4    
    Stats-Aggr Operator 

  Stage: Stage-2    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            Reduce Output Operator  
              key expressions: _col3 (type: string), _col15 (type: string)  
              sort order: ++    
              Map-reduce partition columns: _col3 (type: string), _col15 (type: string) 
              Statistics: Num rows: 4024547 Data size: 7356871916 Basic stats: COMPLETE Column stats: PARTIAL   
              value expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col13 (type: int), _col14 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string)    
          TableScan 
            alias: b    
            Statistics: Num rows: 101549 Data size: 2741823 Basic stats: COMPLETE Column stats: NONE    
            Reduce Output Operator  
              key expressions: answer_id (type: string), insert_time (type: string) 
              sort order: ++    
              Map-reduce partition columns: answer_id (type: string), insert_time (type: string)    
              Statistics: Num rows: 101549 Data size: 2741823 Basic stats: COMPLETE Column stats: NONE  
      Reduce Operator Tree: 
        Join Operator   
          condition map:    
               Left Outer Join0 to 1    
          keys: 
            0 _col3 (type: string), _col15 (type: string)   
            1 answer_id (type: string), insert_time (type: string)  
          outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27, _col31   
          Statistics: Num rows: 4427001 Data size: 8092559283 Basic stats: COMPLETE Column stats: NONE  
          Filter Operator   
            predicate: _col31 is null (type: boolean)   
            Statistics: Num rows: 2213500 Data size: 4046278727 Basic stats: COMPLETE Column stats: NONE    
            Select Operator 
              expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col3 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col13 (type: int), _col14 (type: string), _col15 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string) 
              outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
              Statistics: Num rows: 2213500 Data size: 4046278727 Basic stats: COMPLETE Column stats: NONE  
              File Output Operator  
                compressed: false   
                table:  
                    input format: org.apache.hadoop.mapred.SequenceFileInputFormat  
                    output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat    
                    serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe 

  Stage: Stage-1    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            alias: zhihu.zhihu_answer   
            filterExpr: ym is not null (type: boolean)  
            Statistics: Num rows: 76466394 Data size: 16134409134 Basic stats: COMPLETE Column stats: PARTIAL   
            Reduce Output Operator  
              key expressions: ym (type: string)    
              sort order: + 
              Map-reduce partition columns: ym (type: string)   
              Statistics: Num rows: 76466394 Data size: 16134409134 Basic stats: COMPLETE Column stats: PARTIAL 
              value expressions: admin_closed_comment (type: boolean), answer_content (type: string), answer_created (type: string), answer_id (type: string), answer_updated (type: string), author_headline (type: string), author_id (type: string), author_name (type: string), author_type (type: string), author_url_token (type: string), avatar_url (type: string), badge_num (type: smallint), can_comment (type: boolean), comment_count (type: int), gender (type: string), insert_time (type: string), is_advertiser (type: boolean), is_collapsed (type: boolean), is_copyable (type: boolean), is_org (type: boolean), question_created (type: string), question_id (type: string), question_title (type: string), question_type (type: string), reward_member_count (type: int), reward_total_money (type: int), voteup_count (type: int)    
          TableScan 
            Reduce Output Operator  
              key expressions: _col0 (type: string) 
              sort order: + 
              Map-reduce partition columns: _col0 (type: string)    
              Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE   
      Reduce Operator Tree: 
        Join Operator   
          condition map:    
               Left Semi Join 0 to 1    
          keys: 
            0 ym (type: string) 
            1 _col0 (type: string)  
          outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
          Statistics: Num rows: 4024547 Data size: 7356871916 Basic stats: COMPLETE Column stats: PARTIAL   
          File Output Operator  
            compressed: false   
            table:  
                input format: org.apache.hadoop.mapred.SequenceFileInputFormat  
                output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat    
                serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe

@leftjoin的hql解释：

Explain 
STAGE DEPENDENCIES: 
  Stage-3 is a root stage   
  Stage-6 depends on stages: Stage-3 , consists of Stage-7, Stage-1 
  Stage-7 has a backup stage: Stage-1   
  Stage-5 depends on stages: Stage-7    
  Stage-2 depends on stages: Stage-1, Stage-5   
  Stage-1   
  Stage-0 depends on stages: Stage-2    

STAGE PLANS:    
  Stage: Stage-3    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            alias: zhihu_answer_increment   
            filterExpr: ym is not null (type: boolean)  
            Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: COMPLETE   
            Select Operator 
              expressions: ym (type: string)    
              outputColumnNames: ym 
              Statistics: Num rows: 101549 Data size: 21426839 Basic stats: COMPLETE Column stats: COMPLETE 
              Group By Operator 
                keys: ym (type: string) 
                mode: hash  
                outputColumnNames: _col0    
                Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE 
                Reduce Output Operator  
                  key expressions: _col0 (type: string) 
                  sort order: + 
                  Map-reduce partition columns: _col0 (type: string)    
                  Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE   
      Execution mode: vectorized    
      Reduce Operator Tree: 
        Group By Operator   
          keys: KEY._col0 (type: string)    
          mode: mergepartial    
          outputColumnNames: _col0  
          Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE   
          Group By Operator 
            keys: _col0 (type: string)  
            mode: hash  
            outputColumnNames: _col0    
            Statistics: Num rows: 1 Data size: 184 Basic stats: COMPLETE Column stats: COMPLETE 
            File Output Operator    
              compressed: false 
              table:    
                  input format: org.apache.hadoop.mapred.SequenceFileInputFormat    
                  output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat  
                  serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe   

  Stage: Stage-6    
    Conditional Operator    

  Stage: Stage-7    
    Map Reduce Local Work   
      Alias -> Map Local Tables:    
        s:s-subquery1:$INTNAME  
          Fetch Operator    
            limit: -1   
      Alias -> Map Local Operator Tree: 
        s:s-subquery1:$INTNAME  
          TableScan 
            HashTable Sink Operator 
              keys: 
                0 ym (type: string) 
                1 _col0 (type: string)  

  Stage: Stage-5    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            alias: t    
            filterExpr: ym is not null (type: boolean)  
            Statistics: Num rows: 76466394 Data size: 16134409134 Basic stats: COMPLETE Column stats: PARTIAL   
            Map Join Operator   
              condition map:    
                   Left Semi Join 0 to 1    
              keys: 
                0 ym (type: string) 
                1 _col0 (type: string)  
              outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27   
              Statistics: Num rows: 4024547 Data size: 7340773728 Basic stats: COMPLETE Column stats: PARTIAL   
              Select Operator   
                expressions: _col0 (type: boolean), _col1 (type: string), _col2 (type: string), _col3 (type: string), _col4 (type: string), _col5 (type: string), _col6 (type: string), _col7 (type: string), _col8 (type: string), _col9 (type: string), _col10 (type: string), _col11 (type: smallint), _col12 (type: boolean), _col14 (type: string), _col15 (type: string), _col16 (type: boolean), _col17 (type: boolean), _col18 (type: boolean), _col19 (type: boolean), _col20 (type: string), _col21 (type: string), _col22 (type: string), _col23 (type: string), _col24 (type: int), _col25 (type: int), _col26 (type: int), _col27 (type: string), 0 (type: int)    
                outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12, _col13, _col14, _col15, _col16, _col17, _col18, _col19, _col20, _col21, _col22, _col23, _col24, _col25, _col26, _col27 
                Statistics: Num rows: 4024547 Data size: 756614836 Basic stats: COMPLETE Column stats: PARTIAL  
                File Output Operator    
                  compressed: false 
                  table:    
                      input format: org.apache.hadoop.mapred.SequenceFileInputFormat    
                      output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat  
                      serde: org.apache.hadoop.hive.serde2.lazybinary.LazyBinarySerDe   
      Local Work:   
        Map Reduce Local Work   

  Stage: Stage-2    
    Map Reduce  
      Map Operator Tree:    
          TableScan 
            Union

2条答案

按热度按时间

70gysomp1#

set hive.auto.convert.join=true; --this enables map-join
set hive.mapjoin.smalltable.filesize=25000000;
set hive.execution.engine=tez;

insert overwrite table zhihu.answer partition(ym)
select col1, col2 ... coln, ym, --list all columns
from
(
select col1, col2 ... coln, ym, --list all columns
       row_number() over(partition by ym, answer_id, insert_time order by new_flag desc) rn
from
 (
     select col1, col2 ... coln, ym, --list all columns
            0 as new_flag
       from zhihu.answer t
      where t.ym in (select distinct ym from zhihu.answer_increment)

   UNION ALL 

     select col1, col2 ... coln, ym, --list all columns
            1 as new_flag
       from zhihu.answer_increment t 
 )s
)s
where s.rn=1;

索引在hive3.0中被删除，更多细节见jira:hive-18448
另请参见以下答案：https://stackoverflow.com/a/37744071/2700344
同时调整并行性以获得更好的性能：https://stackoverflow.com/a/48487306/2700344
更新：我研究了@dennisli提供的计划。一些观察结果：
大表与整个增量表的连接作为Map连接执行。在这种情况下，完全连接方法可能比union all+row\ U number更好。
带有分区列表的连接已经被优化器转换为左半连接（也可以作为Map连接），过滤后总共70m中有4k行。我建议分别计算最小和最大增量ym分区，并将它们作为参数传递，其中ym>=${min\u increment\u ym}和ym<=${max\u increment\u ym}在这种情况下，分区修剪将有效地过滤数据，而无需连接。但它只能应用于increment数据集（increment包含单个小范围的分区，我们可以有效地使用min和max），实现它将给您带来最大的好处
未启用中间压缩。启用压缩可能会给您带来一些好处，但值得一试
推荐方法：

set hive.auto.convert.join=true; --this enables map-join
set hive.mapjoin.smalltable.filesize=25000000;

--check compression influence separately.
--it may give some improvement depending on your data entropy
set hive.exec.compress.intermediate=true;
set mapred.output.compress=true;
set hive.exec.compress.output=true;

insert overwrite table zhihu.answer partition(ym)
 select --select increment if exists, old if not exists
  case when i.answer_id is not null then i.col1 else t.col1 end as col1,
  ... --for all columns
  case when i.answer_id is not null then i.coln else t.coln end as coln,
  --partition is the last one
  case when i.answer_id is not null then i.ym else t.ym end as ym
   from zhihu.answer t
        full join zhihu.answer_increment i
        on t.answer_id   = i.answer_id
       and t.insert_time = i.insert_time
       and t.ym=i.ym --check this condition
  where t.ym in (select distinct ym from zhihu.answer_increment) --try to implement min and max parameters instead of this if possible (see 2)
  --alternatively if you do not want to employ shell, check if you can
  --remove the WHERE condition providing ym in the join condition, 
  --this will allow to get rid of the second join in the plan, 
  --though partition pruning will work with parameters better 
;

最后，该方案将是最理想的方案。
您可能仍然需要根据执行日志调整Map器和还原器上的并行性，请参阅前面的答案建议

赞(0）回复(0）举报 2021-06-26

izkcnapc2#

你能做的事情很少
尝试在第一个查询中使用left-semi-join。
由于您的表zhihu.answer\u增量非常小，相比之下您可以尝试给出map side连接提示
如果您的表是在同一列上加扣的，并且两个扣都是相同的，请尝试使用smb方法
尝试设置以下属性
设置hive.exec.compress.intermediate=true；
设置hive.exec.parallel=true；
设置hive.exec.parallel.thread.number=50；

hive如何提高查询性能？

2条答案

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