Question

我将表存储为SequenceFile格式，我设置以下命令以启用带有BLOCK压缩的序列 -

set mapred.output.compress=true;
set mapred.output.compression.type=BLOCK;
set mapred.output.compression.codec=org.apache.hadoop.io.compress.LzoCodec;

但是当我尝试查看这样的表格时 -

describe extended lip_table

我得到以下信息，其中有一个名为compressed的字段设置为false，这意味着我的数据没有通过设置上述三个命令来压缩？

Detailed Table Information      Table(tableName:lip_table, dbName:default, owner:uname, 
createTime:1343931235, lastAccessTime:0, retention:0, sd:StorageDescriptor(cols:
[FieldSchema(name:buyer_id, type:bigint, comment:null), FieldSchema(name:total_chkout, 
type:bigint, comment:null), FieldSchema(name:total_errpds, type:bigint, comment:null)], 
location:hdfs://ares-nn/apps/hdmi/uname/lip-data, 
inputFormat:org.apache.hadoop.mapred.SequenceFileInputFormat, 
outputFormat:org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat, 
**compressed:false**, numBuckets:-1, serdeInfo:SerDeInfo(name:null, 
serializationLib:org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, parameters:
{serialization.format=   , field.delim=

Answer 1

我发现我认为this article可以解决您的问题。您应该尝试在创建表或使用ALTER语句时在表定义级别指定压缩编解码器的用法。

创建时：

 CREATE EXTERNAL TABLE lip_table (
                                    column1 string
                                  , column2 string 
                                 )
PARTITIONED BY (date string)
ROW FORMAT DELIMITED FIELDS TERMINATED BY "\t"
STORED AS INPUTFORMAT "com.hadoop.mapred.DeprecatedLzoTextInputFormat"
          OUTPUTFORMAT "org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat"
LOCATION '/path/to/hive/tables/lip';

使用ALTER（仅影响随后创建的分区）：

ALTER TABLE lip_table
SET FILEFORMAT
    INPUTFORMAT "com.hadoop.mapred.DeprecatedLzoTextInputFormat"
    OUTPUTFORMAT "org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat";

http://www.mrbalky.com/2011/02/24/hive-tables-partitions-and-lzo-compression/

Answer 2

要避免serde例外，也要使用serde类。

ALTER TABLE <<table name>>
SET FILEFORMAT
INPUTFORMAT "<<Input format class>>"
OUTPUTFORMAT
"<<Output format class>>" SERDE "<<Serde class>>";

描述Hive中的扩展表

2 个答案: