August 2015
Intermediate to advanced
312 pages
7h 28m
Japanese
Content preview from 初めてのSpark
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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.
185
9.5 ユーザー定義関数
9.5.1
Spark SQL
の
UDF
Spark SQL
には、サポートされている言語で書かれた関数を渡し、簡単に
UDF
を登録できる組
み込みメソッドが用意されています。
Scala
および
Python
では、言語の持つネイティブの関数と
ラムダ式を使います。
Java
の場合は、適切な
UDF
のクラスを拡張するだけです。
UDF
は多種類
の型を扱うことができ、呼び出された際のデータとは異なる型のデータを返すことができます。
Python
および
Java
では、
9-1
中の
SchemaRDD
のいずれかの型を使い、返値の型を指定し
なければなりません。これらの型は、
Java
では
org.apache.spark.sql.api.java.DataType
にあり
ます。
Python
の場合は、
DataType
をインポートします。
9-36
と
9-37
では、きわめてシンプルな
UDF
を使って文字列の長さを計算して
います。この
UDF
は、使用しているツイートの長さを求めるために使うことができます。
9-36
Python
UDF
#
返す型である
IntegerType
をインポート
from pyspark.sql.types import IntegerType
#
テキストの長さを返す
UDF
の作成
hiveCtx.registerFunction("strLenPython", lambda x: len(x), IntegerType())
lengthSchemaRDD = ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
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.