hive上可以使用多种格式，比如纯文本，lzo、orc等，为了搞清楚它们之间的关系，特意做个测试。

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一、建立样例表

hive> create table tbl( id int, name string ) row format delimited fields terminated by '|' stored as textfile;

OK

Time taken: 0.338 seconds

hive> load data local inpath '/home/grid/users.txt' into table tbl;

Copying data from file:/home/grid/users.txt

Copying file: file:/home/grid/users.txt

Loading data to table default.tbl

Table default.tbl stats: [numFiles=1, numRows=0, totalSize=111, rawDataSize=0]

OK

Time taken: 0.567 seconds

hive> select * from tbl;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.237 seconds, Fetched: 14 row(s)

 

二、测试写入

1、无压缩

hive> set hive.exec.compress.output;

hive.exec.compress.output=false

hive>

>

> create table tbltxt as select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498527794024_0001, Tracking URL = http://hadoop1:8088/proxy/application_1498527794024_0001/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498527794024_0001

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-27 10:55:29,906 Stage-1 map = 0%,  reduce = 0%

2017-06-27 10:55:39,532 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 2.66 sec

MapReduce Total cumulative CPU time: 2 seconds 660 msec

Ended Job = job_1498527794024_0001

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-27_10-55-18_962_2187345348997213497-1/-ext-10001

Moving data to: hdfs://hadoop1:9000/user/hive/warehouse/tbltxt

Table default.tbltxt stats: [numFiles=1, numRows=14, totalSize=111, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 2.66 sec   HDFS Read: 318 HDFS Write: 181 SUCCESS

Total MapReduce CPU Time Spent: 2 seconds 660 msec

OK

Time taken: 22.056 seconds

hive>

> show create table tbltxt;

OK

CREATE  TABLE `tbltxt`(

`id` int,

`name` string)

ROW FORMAT SERDE

'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'

STORED AS INPUTFORMAT

'org.apache.hadoop.mapred.TextInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

LOCATION

'hdfs://hadoop1:9000/user/hive/warehouse/tbltxt'

TBLPROPERTIES (

'COLUMN_STATS_ACCURATE'='true',

'numFiles'='1',

'numRows'='14',

'rawDataSize'='97',

'totalSize'='111',

'transient_lastDdlTime'='1498532140')

Time taken: 0.202 seconds, Fetched: 18 row(s)

hive>

>

> select * from tbltxt;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.059 seconds, Fetched: 14 row(s)

hive>

>

> dfs -ls /user/hive/warehouse/tbltxt;

Found 1 items

-rwxr-xr-x   1 grid supergroup        111 2017-06-27 10:55 /user/hive/warehouse/tbltxt/000000_0

hive>

>

> dfs -cat /user/hive/warehouse/tbltxt/000000_0;

1Awyp

2Azs

3Als

4Aww

5Awyp2

6Awyp3

7Awyp4

8Awyp5

9Awyp6

10Awyp7

11Awyp8

12Awyp5

13Awyp9

14Awyp20

读取和写入的格式为：

STORED AS INPUTFORMAT

'org.apache.hadoop.mapred.TextInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

数据可以正常读出，数据格式为纯文本，可以直接用cat查看

2、使用压缩，格式为默认的压缩

hive>

> set hive.exec.compress.output=true;

hive>

>

> set mapred.output.compression.codec;

mapred.output.compression.codec=org.apache.hadoop.io.compress.DefaultCodec

可见当前压缩格式为默认的DefaultCodec。

hive>

> create table tbldefault as select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498527794024_0002, Tracking URL = http://hadoop1:8088/proxy/application_1498527794024_0002/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498527794024_0002

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-27 11:14:44,845 Stage-1 map = 0%,  reduce = 0%

2017-06-27 11:14:48,964 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 1.08 sec

MapReduce Total cumulative CPU time: 1 seconds 80 msec

Ended Job = job_1498527794024_0002

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-27_11-14-39_351_6035948930260680086-1/-ext-10001

Moving data to: hdfs://hadoop1:9000/user/hive/warehouse/tbldefault

Table default.tbldefault stats: [numFiles=1, numRows=14, totalSize=76, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 1.08 sec   HDFS Read: 318 HDFS Write: 150 SUCCESS

Total MapReduce CPU Time Spent: 1 seconds 80 msec

OK

Time taken: 10.842 seconds

hive>

>

> show create table tbldefault;

OK

CREATE  TABLE `tbldefault`(

`id` int,

`name` string)

ROW FORMAT SERDE

'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'

STORED AS INPUTFORMAT

'org.apache.hadoop.mapred.TextInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

LOCATION

'hdfs://hadoop1:9000/user/hive/warehouse/tbldefault'

TBLPROPERTIES (

'COLUMN_STATS_ACCURATE'='true',

'numFiles'='1',

'numRows'='14',

'rawDataSize'='97',

'totalSize'='76',

'transient_lastDdlTime'='1498533290')

Time taken: 0.044 seconds, Fetched: 18 row(s)

hive>

>

> select * from tbldefault;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.037 seconds, Fetched: 14 row(s)

hive>

>

> dfs -ls /user/hive/warehouse/tbldefault;

Found 1 items

-rwxr-xr-x   1 grid supergroup         76 2017-06-27 11:14 /user/hive/warehouse/tbldefault/000000_0.deflate

hive>

> dfs -cat /user/hive/warehouse/tbldefault/000000_0.deflate;

xws

dfX0)60K:HBhive>

>

>

可见在默认压缩下，表的读写格式与txt一样，但数据文件是经过默认库压缩的，后缀名为deflate，用户无法直接查看内容。意味着org.apache.hadoop.mapred.TextInputFormat这种input可以根据后缀识别默认压缩，并读出内容。

3、lzo压缩

hive>

> set mapred.output.compression.codec=com.hadoop.compression.lzo.LzoCodec;

hive>

>

> create table tbllzo as select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498527794024_0003, Tracking URL = http://hadoop1:8088/proxy/application_1498527794024_0003/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498527794024_0003

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-27 11:29:08,436 Stage-1 map = 0%,  reduce = 0%

2017-06-27 11:29:14,638 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 1.87 sec

MapReduce Total cumulative CPU time: 1 seconds 870 msec

Ended Job = job_1498527794024_0003

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-27_11-29-03_249_4340474818139134521-1/-ext-10001

Moving data to: hdfs://hadoop1:9000/user/hive/warehouse/tbllzo

Table default.tbllzo stats: [numFiles=1, numRows=14, totalSize=106, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 1.87 sec   HDFS Read: 318 HDFS Write: 176 SUCCESS

Total MapReduce CPU Time Spent: 1 seconds 870 msec

OK

Time taken: 13.744 seconds

hive>

>

> show create table tbllzo;

OK

CREATE  TABLE `tbllzo`(

`id` int,

`name` string)

ROW FORMAT SERDE

'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'

STORED AS INPUTFORMAT

'org.apache.hadoop.mapred.TextInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

LOCATION

'hdfs://hadoop1:9000/user/hive/warehouse/tbllzo'

TBLPROPERTIES (

'COLUMN_STATS_ACCURATE'='true',

'numFiles'='1',

'numRows'='14',

'rawDataSize'='97',

'totalSize'='106',

'transient_lastDdlTime'='1498534156')

Time taken: 0.044 seconds, Fetched: 18 row(s)

hive>

> select * from tbllzo;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.032 seconds, Fetched: 14 row(s)

hive>

>

> dfs -ls /user/hive/warehouse/tbllzo;

Found 1 items

-rwxr-xr-x   1 grid supergroup        106 2017-06-27 11:29 /user/hive/warehouse/tbllzo/000000_0.lzo_deflate

hive>

>

> dfs -cat /user/hive/warehouse/tbllzo/000000_0.lzo_deflate;

ob1Awyp

2Azs

3Als

4Aww

5Awyp2

6

7

8

9

10

1

125

13Awyp9

14Awyp20

在lz压缩下，表的读写格式仍然是org.apache.hadoop.mapred.TextInputFormat，数据文件后缀名为.lzo_deflate，用户无法直接查看内容。也就是说，org.apache.hadoop.mapred.TextInputFormat这种input可以识别lzo压缩并读出内容。（真强大！）

4、lzop压缩

hive>

> set mapred.output.compression.codec=com.hadoop.compression.lzo.LzopCodec;

hive>

> create table tbllzop as select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498527794024_0004, Tracking URL = http://hadoop1:8088/proxy/application_1498527794024_0004/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498527794024_0004

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-27 11:37:28,010 Stage-1 map = 0%,  reduce = 0%

2017-06-27 11:37:32,127 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 2.1 sec

MapReduce Total cumulative CPU time: 2 seconds 100 msec

Ended Job = job_1498527794024_0004

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-27_11-37-23_099_3493082162039010112-1/-ext-10001

Moving data to: hdfs://hadoop1:9000/user/hive/warehouse/tbllzop

Table default.tbllzop stats: [numFiles=1, numRows=14, totalSize=148, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 2.1 sec   HDFS Read: 318 HDFS Write: 219 SUCCESS

Total MapReduce CPU Time Spent: 2 seconds 100 msec

OK

Time taken: 10.233 seconds

hive>

>

> show create table tbllzop;

OK

CREATE  TABLE `tbllzop`(

`id` int,

`name` string)

ROW FORMAT SERDE

'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'

STORED AS INPUTFORMAT

'org.apache.hadoop.mapred.TextInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'

LOCATION

'hdfs://hadoop1:9000/user/hive/warehouse/tbllzop'

TBLPROPERTIES (

'COLUMN_STATS_ACCURATE'='true',

'numFiles'='1',

'numRows'='14',

'rawDataSize'='97',

'totalSize'='148',

'transient_lastDdlTime'='1498534653')

Time taken: 0.046 seconds, Fetched: 18 row(s)

hive>

>

>

> select * from tbllzop;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.033 seconds, Fetched: 14 row(s)

hive>

>

> dfs -ls /user/hive/warehouse/tbllzop;

Found 1 items

-rwxr-xr-x   1 grid supergroup        148 2017-06-27 11:37 /user/hive/warehouse/tbllzop/000000_0.lzo

hive>

>

> dfs -cat /user/hive/warehouse/tbllzop/000000_0.lzo;

          ob1Awyp

2Azs

3Als

4Aww

5Awyp2

6

7

8

9

10

1

125

13Awyp9

14Awyp20

同样，在lzop压缩下，表的读写格式仍然是org.apache.hadoop.mapred.TextInputFormat，数据文件后缀名为.lzo，用户无法直接查看内容。org.apache.hadoop.mapred.TextInputFormat可以识别lzop压缩并读出内容

从以上几种情况可以看出，不管使用哪种压缩，在hive看来都属于纯文本（只是使用了不同方法压缩而已），使用org.apache.hadoop.mapred.TextInputFormat都可以读取，而且hive在插入时只会根据mapred.output.compression.codec来压缩（而不会管表定义的inputFormat是什么）。以下可以验证一下：

1、set mapred.output.compression.codec=com.hadoop.compression.lzo.LzopCodec时插入数据，数据文件是lzop的压缩，且可以正常读出。

hive> set mapred.output.compression.codec=com.hadoop.compression.lzo.LzopCodec;

hive>

> create table tbltest1( id int, name string )

> stored as inputformat 'org.apache.hadoop.mapred.TextInputFormat'

> outputformat 'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat';

OK

Time taken: 0.493 seconds

hive>

> insert into table tbltest1 select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498660018952_0001, Tracking URL = http://hadoop1:8088/proxy/application_1498660018952_0001/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498660018952_0001

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-28 22:59:27,886 Stage-1 map = 0%,  reduce = 0%

2017-06-28 22:59:36,427 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 2.25 sec

MapReduce Total cumulative CPU time: 2 seconds 250 msec

Ended Job = job_1498660018952_0001

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-28_22-59-14_730_4437480099583255943-1/-ext-10000

Loading data to table default.tbltest1

Table default.tbltest1 stats: [numFiles=1, numRows=14, totalSize=148, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 2.25 sec   HDFS Read: 318 HDFS Write: 220 SUCCESS

Total MapReduce CPU Time Spent: 2 seconds 250 msec

OK

Time taken: 24.151 seconds

hive>

> dfs -ls /user/hive/warehouse/tbltest1;

Found 1 items

-rwxr-xr-x   1 grid supergroup        148 2017-06-28 22:59 /user/hive/warehouse/tbltest1/000000_0.lzo

hive>

> select * from tbltest1;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.055 seconds, Fetched: 14 row(s)

2、set mapred.output.compression.codec=org.apache.hadoop.io.compress.DefaultCodec时插入数据，数据文件是默认的压缩，且可以正常读出。

hive> set mapred.output.compression.codec=org.apache.hadoop.io.compress.DefaultCodec;

hive> create table tbltest2( id int, name string )

> stored as inputformat 'org.apache.hadoop.mapred.TextInputFormat'

> outputformat 'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat';

OK

Time taken: 0.142 seconds

hive> insert into table tbltest2 select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498660018952_0002, Tracking URL = http://hadoop1:8088/proxy/application_1498660018952_0002/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498660018952_0002

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-28 23:09:06,439 Stage-1 map = 0%,  reduce = 0%

2017-06-28 23:09:11,668 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 1.15 sec

MapReduce Total cumulative CPU time: 1 seconds 150 msec

Ended Job = job_1498660018952_0002

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-28_23-09-01_674_9172062679713398655-1/-ext-10000

Loading data to table default.tbltest2

Table default.tbltest2 stats: [numFiles=1, numRows=14, totalSize=76, rawDataSize=97]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 1.15 sec   HDFS Read: 318 HDFS Write: 148 SUCCESS

Total MapReduce CPU Time Spent: 1 seconds 150 msec

OK

Time taken: 11.278 seconds

hive>

>

>

> dfs -ls /user/hive/warehouse/tbltest2;

Found 1 items

-rwxr-xr-x   1 grid supergroup         76 2017-06-28 23:09 /user/hive/warehouse/tbltest2/000000_0.deflate

hive>

> select * from tbltest2;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.035 seconds, Fetched: 14 row(s)

3、当表是orc格式时，会按照ORC格式进行压缩，不受mapred.output.compression.codec和hive.exec.compress.output影响。

hive>  set hive.exec.compress.output=false;

hive> create table tbltest3( id int, name string )

> stored as orc tblproperties("orc.compress"="SNAPPY");

OK

Time taken: 0.08 seconds

hive>  insert into table tbltest3 select * from tbl;

Total jobs = 3

Launching Job 1 out of 3

Number of reduce tasks is set to 0 since there's no reduce operator

Starting Job = job_1498660018952_0003, Tracking URL = http://hadoop1:8088/proxy/application_1498660018952_0003/

Kill Command = /opt/hadoop/bin/hadoop job  -kill job_1498660018952_0003

Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 0

2017-06-28 23:30:29,865 Stage-1 map = 0%,  reduce = 0%

2017-06-28 23:30:34,007 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 1.14 sec

MapReduce Total cumulative CPU time: 1 seconds 140 msec

Ended Job = job_1498660018952_0003

Stage-4 is selected by condition resolver.

Stage-3 is filtered out by condition resolver.

Stage-5 is filtered out by condition resolver.

Moving data to: hdfs://hadoop1:9000/tmp/hive-grid/hive_2017-06-28_23-30-25_350_7458831371800658041-1/-ext-10000

Loading data to table default.tbltest3

Table default.tbltest3 stats: [numFiles=1, numRows=14, totalSize=365, rawDataSize=1288]

MapReduce Jobs Launched:

Stage-Stage-1: Map: 1   Cumulative CPU: 1.14 sec   HDFS Read: 318 HDFS Write: 439 SUCCESS

Total MapReduce CPU Time Spent: 1 seconds 140 msec

OK

Time taken: 9.963 seconds

hive> dfs -ls /user/hive/warehouse/tbltest3;

Found 1 items

-rwxr-xr-x   1 grid supergroup        365 2017-06-28 23:30 /user/hive/warehouse/tbltest3/000000_0

hive>

> dfs -cat /user/hive/warehouse/tbltest3/000000_0;

ORC

)

9

"

A+_Az_

+@DA+y-Az_A+_A++A+y-2345678,5A+y-9A+y-20

hive>

> show create table tbltest3;

OK

CREATE  TABLE `tbltest3`(

`id` int,

`name` string)

ROW FORMAT SERDE

'org.apache.hadoop.hive.ql.io.orc.OrcSerde'

STORED AS INPUTFORMAT

'org.apache.hadoop.hive.ql.io.orc.OrcInputFormat'

OUTPUTFORMAT

'org.apache.hadoop.hive.ql.io.orc.OrcOutputFormat'

LOCATION

'hdfs://hadoop1:9000/user/hive/warehouse/tbltest3'

TBLPROPERTIES (

'COLUMN_STATS_ACCURATE'='true',

'numFiles'='1',

'numRows'='14',

'orc.compress'='SNAPPY',

'rawDataSize'='1288',

'totalSize'='365',

'transient_lastDdlTime'='1498663835')

Time taken: 0.217 seconds, Fetched: 19 row(s)

hive>

> select * from tbltest3;

OK

1       Awyp

2       Azs

3       Als

4       Aww

5       Awyp2

6       Awyp3

7       Awyp4

8       Awyp5

9       Awyp6

10      Awyp7

11      Awyp8

12      Awyp5

13      Awyp9

14      Awyp20

Time taken: 0.689 seconds, Fetched: 14 row(s)

可见当orc格式时，插入数据并不受压缩参数的影响。而且inputformat和outputformat已经不再是text。

三、总结

1、不管是无压缩，还是默认压缩，还是lzo和lzop等格式，对hive来说都是文本格式，可以根据数据文件的后缀名自动识别，写入时根据参数决定是否压缩以及压缩成什么格式

2、orc对hive来说是另外一种格式，不管参数如何指定，都会按照建表语名指定的格式来读取和写入。

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