您好我需要从 gz.parquet 文件中读取数据但不知道如何？尝试使用 impala，但我得到的结果与parquet-tools cat没有表结构的结果相同。
PS：欢迎提出任何改进 Spark 代码的建议。
gz.parquet由于 twitter => flume => kafka => spark streaming => hive/gz.parquet files 创建的数据管道，我有以下 parquet 文件。对于我正在使用的水槽代理agent1.sources.twitter-data.type = org.apache.flume.source.twitter.TwitterSource
Spark 代码从 kafka 中取出数据并存储在 hive 中，如下所示：
val sparkConf = new SparkConf().setAppName("KafkaTweet2Hive")
val sc = new SparkContext(sparkConf)
val ssc = new StreamingContext(sc, Seconds(2))
val sqlContext = new org.apache.spark.sql.hive.HiveContext(sc)//new org.apache.spark.sql.SQLContext(sc)
// Create direct kafka stream with brokers and topics
val topicsSet = topics.split(",").toSet
val kafkaParams = Map[String, String]("metadata.broker.list" -> brokers)
val messages = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder](ssc, kafkaParams, topicsSet)
// Get the data (tweets) from kafka
val tweets = messages.map(_._2)
// adding the tweets to Hive
tweets.foreachRDD { rdd =>
val hiveContext = SQLContext.getOrCreate(rdd.sparkContext)
import sqlContext.implicits._
val tweetsDF = rdd.toDF()
tweetsDF.write.mode("append").saveAsTable("tweet")
}
当我运行spark-streaming应用程序时，它将数据作为gz.parquet文件存储在 hdfs:/user/hive/warehouse目录中，如下所示：
[root@quickstart /]# hdfs dfs -ls /user/hive/warehouse/tweets
Found 469 items
-rw-r--r-- 1 root supergroup 0 2016-03-30 08:36 /user/hive/warehouse/tweets/_SUCCESS
-rw-r--r-- 1 root supergroup 241 2016-03-30 08:36 /user/hive/warehouse/tweets/_common_metadata
-rw-r--r-- 1 root supergroup 35750 2016-03-30 08:36 /user/hive/warehouse/tweets/_metadata
-rw-r--r-- 1 root supergroup 23518 2016-03-30 08:33 /user/hive/warehouse/tweets/part-r-00000-0133fcd1-f529-4dd1-9371-36bf5c3e5df3.gz.parquet
-rw-r--r-- 1 root supergroup 9552 2016-03-30 08:33 /user/hive/warehouse/tweets/part-r-00000-02c44f98-bfc3-47e3-a8e7-62486a1a45e7.gz.parquet
-rw-r--r-- 1 root supergroup 19228 2016-03-30 08:25 /user/hive/warehouse/tweets/part-r-00000-0321ce99-9d2b-4c52-82ab-a9ed5f7d5036.gz.parquet
-rw-r--r-- 1 root supergroup 241 2016-03-30 08:25 /user/hive/warehouse/tweets/part-r-00000-03415df3-c719-4a3a-90c6 462c43cfef54.gz.parquet
文件中的架构_metadata如下：
[root@quickstart /]# parquet-tools meta hdfs://quickstart.cloudera:8020/user/hive/warehouse/tweets/_metadata
creator: parquet-mr version 1.5.0-cdh5.5.0 (build ${buildNumber})
extra: org.apache.spark.sql.parquet.row.metadata = {"type":"struct","fields":[{"name":"tweet","type":"string","nullable":true,"metadata":{}}]}
file schema: root
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
tweet: OPTIONAL BINARY O:UTF8 R:0 D:1
Furthermore, if i load the data into a dataframe in spark i get the output of `df.show´ as follows:
+--------------------+
| tweet|
+--------------------+
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|ڕObjavro.sch...|
|��Objavro.sc...|
|ֲObjavro.sch...|
|��Objavro.sc...|
|��Objavro.sc...|
|֕Objavro.sch...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
|��Objavro.sc...|
+--------------------+
only showing top 20 rows
How ever i would like to see the tweets as plain text?