Hortonworks HDPCD 問題集

質問 1：
You need to create a job that does frequency analysis on input data. You will do this by writing a Mapper that uses TextInputFormat and splits each value (a line of text from an input file) into individual characters. For each one of these characters, you will emit the character as a key and an InputWritable as the value. As this will produce proportionally more intermediate data than input data, which two resources should you expect to be bottlenecks?
A. Processor and disk I/O
B. Disk I/O and network I/O
C. Processor and RAM
D. Processor and network I/O
正解：B

質問 2：
You have user profile records in your OLPT database, that you want to join with web logs you have already ingested into the Hadoop file system. How will you obtain these user records?
A. Sqoop import
B. HDFS command
C. Ingest with Hadoop Streaming
D. Ingest with Flume agents
E. Hive LOAD DATA command
F. Pig LOAD command
正解：A
解説: (Topexam メンバーにのみ表示されます)

質問 3：
Which one of the following is NOT a valid Oozie action?
A. hive
B. mapreduce
C. mrunit
D. pig
正解：C

質問 4：
You want to count the number of occurrences for each unique word in the supplied input data. You've decided to implement this by having your mapper tokenize each word and emit a literal value 1, and then have your reducer increment a counter for each literal 1 it receives. After successful implementing this, it occurs to you that you could optimize this by specifying a combiner. Will you be able to reuse your existing Reduces as your combiner in this case and why or why not?
A. Yes, because Java is a polymorphic object-oriented language and thus reducer code can be reused as a combiner.
B. No, because the Combiner is incompatible with a mapper which doesn't use the same data type for both the key and value.
C. No, because the Reducer and Combiner are separate interfaces.
D. Yes, because the sum operation is both associative and commutative and the input and output types to the reduce method match.
E. No, because the sum operation in the reducer is incompatible with the operation of a Combiner.
正解：D
解説: (Topexam メンバーにのみ表示されます)

質問 5：
When can a reduce class also serve as a combiner without affecting the output of a MapReduce program?
A. When the signature of the reduce method matches the signature of the combine method.
B. Always. The point of a combiner is to serve as a mini-reducer directly after the map phase to increase performance.
C. Always. Code can be reused in Java since it is a polymorphic object-oriented programming language.
D. When the types of the reduce operation's input key and input value match the types of the reducer's output key and output value and when the reduce operation is both communicative and associative.
E. Never. Combiners and reducers must be implemented separately because they serve different purposes.
正解：D
解説: (Topexam メンバーにのみ表示されます)

質問 6：
A NameNode in Hadoop 2.2 manages ______________.
A. Two namespaces: an active namespace and a backup namespace
B. An arbitrary number of namespaces
C. No namespaces
D. A single namespace
正解：D

質問 7：
A client application creates an HDFS file named foo.txt with a replication factor of 3. Identify which best describes the file access rules in HDFS if the file has a single block that is stored on data nodes A, B and C?
A. The file can be accessed if at least one of the data nodes storing the file is available.
B. The file will be marked as corrupted if data node B fails during the creation of the file.
C. Each data node locks the local file to prohibit concurrent readers and writers of the file.
D. Each data node stores a copy of the file in the local file system with the same name as the HDFS file.
正解：A
解説: (Topexam メンバーにのみ表示されます)

質問 8：
Given the following Hive commands:

Which one of the following statements Is true?
A. The file mydata.txt is copied into Hive's underlying relational database 0.
B. The file mydata.txt is copied to a subfolder of /apps/hive/warehouse
C. The file mydata.txt does not move from Its current location in HDFS
D. The file mydata.txt is moved to a subfolder of /apps/hive/warehouse
正解：B