昨天捣鼓了一天这个东西，随便写点笔记。

• arvo：除了著名的hdfs文件，hadoop上常用的另一种序列化存储的文件格式就是arvo。简单的讲，这货就是由一个定义好的schema来读取的二进制文本文件。
• arvo schema：很像json...比如这里这个：

{
 "type" : "record",
 "name" : "Tweet",
 "namespace" : "com.miguno.avro",
 "fields" : [ {
 "name" : "username",
 "type" : "string",
 "doc" : "Name of the user account on Twitter.com"
 }, {
 "name" : "tweet",
 "type" : "string",
 "doc" : "The content of the user's Twitter message"
 }, {
 "name" : "timestamp",
 "type" : "long",
 "doc" : "Unix epoch time in seconds"
 } ],
 "doc:" : "A basic schema for storing Twitter messages"
}

• 定义好schema之后可以用java去build...
• arvo to HIVE：可以直接建HIVE external table. (还是上面那个link)

CREATE EXTERNAL TABLE tweets
 COMMENT "A table backed by Avro data with the Avro schema stored in HDFS"
 ROW FORMAT SERDE 'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
 STORED AS
 INPUTFORMAT 'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat'
 OUTPUTFORMAT 'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat'
 LOCATION '/user/YOURUSER/examples/input/'
 TBLPROPERTIES (
 'avro.schema.url'='hdfs:///user/YOURUSER/examples/schema/twitter.avsc'
 );

然后就是正常的玩法了。