August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
84
5 章 データのロードとセーブ
クラスを変更すると、古いファイルは読めなくなってしまうかもしれません。
5.2.6
Hadoop
の入フーット
Spark
がラッパを持っているフォーマット群に加えて、
Hadoop
がサポートしているフォーマッ
トは、どれも扱うことができます。
Spark
は、
Hadoop
の
API
をどちらもサポートし
ているので、柔軟な対応が可能です
†
。
他の
Hadoop
の入力フォーマットでのロード
新しい
Hadoop
の
API
を使ってファイルを読むには、
Spark
にいくつかの指示をしなければな
りません。
newAPIHadoopFile
は、パスに加えて
3
つのクラスを引数に取ります。最初のクラス
はーで、これは入力フォーマットを表すクラスです。古い
API
で実装された
Hadoop
の入力フォーマットも扱えるよう、同様の関数として
hadoopFile()
があります。次のク
ラスはキーのクラスで、最後のクラスは値のクラスです。
Hadoop
の設定プロパティを追加で指定
する必要がある場合には、
conf
オブジェクトを渡すこともできます。
Hadoop
の入力フォーマットの中でも最もシンプルなものが
KeyValueTextInputFormat
です。
これは、テキストファイルからキー／値のデータを読み取るために使うことができます（
5-24
参照）。各行は独立して処理され、キーと値はタブで区切られます。このフォーマットは
Hadoop
に含まれているので、プロジェクトで使う際に依存対象を追加する必要はありません。 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.