hive基础知识五

Hive 主流文件存储格式对比

1、存储文件的压缩比测试

1.1 测试数据

https://github.com/liufengji/Compression_Format_Data
​
log.txt 大小为18.1 M

1.2 TextFile

• 创建表，存储数据格式为TextFile

create table log_text (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
row format delimited fields terminated by '	'
stored as textfile ;

• 向表中加载数据

load data local inpath '/home/hadoop/log.txt' into table log_text ;

• 查看表的数据量大小

dfs -du -h /user/hive/warehouse/log_text;
​
+------------------------------------------------+--+
|                   DFS Output                   |
+------------------------------------------------+--+
| 18.1 M  /user/hive/warehouse/log_text/log.txt  |
+------------------------------------------------+--+

1.3 Parquet

• 创建表，存储数据格式为 parquet

create table log_parquet  (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
row format delimited fields terminated by '	'
stored as parquet;

• 向表中加载数据

insert into table log_parquet select * from log_text;

• 查看表的数据量大小

hdfs dfs -du -h /user/hive/warehouse/log_parquet;
​
+----------------------------------------------------+--+
|                     DFS Output                     |
+----------------------------------------------------+--+
| 13.1 M  /user/hive/warehouse/log_parquet/000000_0  |
+----------------------------------------------------+--+

1.4 ORC

• 创建表，存储数据格式为ORC

create table log_orc  (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
row format delimited fields terminated by '	'
stored as orc  ;

• 向表中加载数据

insert into table log_orc select * from log_text ;

• 查看表的数据量大小

hdfs dfs -du -h /user/hive/warehouse/log_orc;
+-----------------------------------------------+--+
|                  DFS Output                   |
+-----------------------------------------------+--+
| 2.8 M  /user/hive/warehouse/log_orc/000000_0  |
+-----------------------------------------------+--+

1.5 存储文件的压缩比总结

ORC >  Parquet >  textFile

2、存储文件的查询速度测试

2.1 TextFile

select count(*) from log_text;
+---------+--+
|   _c0   |
+---------+--+
| 100000  |
+---------+--+
1 row selected (16.99 seconds)

2.2 Parquet

select count(*) from log_parquet;
+---------+--+
|   _c0   |
+---------+--+
| 100000  |
+---------+--+
1 row selected (17.994 seconds)

2.3 ORC

select count(*) from log_orc;
+---------+--+
|   _c0   |
+---------+--+
| 100000  |
+---------+--+
1 row selected (15.943 seconds)

2.4 存储文件的查询速度总结

ORC > TextFile > Parquet

3、存储和压缩结合

• 使用压缩的优势是可以最小化所需要的磁盘存储空间，以及减少磁盘和网络io操作

• 官网地址

  • https://cwiki.apache.org/confluence/display/Hive/LanguageManual+ORC

• ORC支持三种压缩：ZLIB,SNAPPY,NONE。最后一种就是不压缩，orc默认采用的是ZLIB压缩。

3.1 创建一个非压缩的的ORC存储方式表

• 1、创建一个非压缩的的ORC表

create table log_orc_none (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
row format delimited fields terminated by '	'
stored as orc tblproperties("orc.compress"="NONE") ;

• 2、加载数据

insert into table log_orc_none select * from log_text ;

• 3、查看表的数据量大小

hdfs dfs -du -h /user/hive/warehouse/log_orc_none;
+----------------------------------------------------+--+
|                     DFS Output                     |
+----------------------------------------------------+--+
| 7.7 M  /user/hive/warehouse/log_orc_none/000000_0  |
+----------------------------------------------------+--+

3.2 创建一个snappy压缩的ORC存储方式表

• 1、创建一个snappy压缩的的ORC表

create table log_orc_snappy (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
row format delimited fields terminated by '	'
stored as orc tblproperties("orc.compress"="SNAPPY") ;

• 2、加载数据

insert into table log_orc_snappy select * from log_text ;

• 3、查看表的数据量大小

hdfs dfs -du -h /user/hive/warehouse/log_orc_snappy;
+------------------------------------------------------+--+
|                      DFS Output                      |
+------------------------------------------------------+--+
| 3.8 M  /user/hive/warehouse/log_orc_snappy/000000_0  |
+------------------------------------------------------+--+

3.3 创建一个ZLIB压缩的ORC存储方式表

• 不指定压缩格式的就是默认的采用ZLIB压缩

  • 可以参考上面创建的 log_orc 表

• 查看表的数据量大小

hdfs dfs -du -h /user/hive/warehouse/log_orc;
+-----------------------------------------------+--+
|                  DFS Output                   |
+-----------------------------------------------+--+
| 2.8 M  /user/hive/warehouse/log_orc/000000_0  |
+-----------------------------------------------+--+

3.4 存储方式和压缩总结

• orc 默认的压缩方式ZLIB比Snappy压缩的还小。

• 在实际的项目开发当中，hive表的数据存储方式一般选择：orc或parquet。

• 由于snappy的压缩和解压缩 效率都比较高，压缩方式一般选择snappy。