Hadoopオンラインテスト

Chusk works as Hadoop developer at Pesla Inc. Chusk is tasked with processing input data to count number of occurrences of each unique word. Chusk did the following to achieve this:

1. Tokenize each word and emit lateral value 1 with Mapper
2. Reducer increments counter for each literal 1 it receives

Chusk is now tasked with optimizing this by using a combiner. Will Chusk be able to reuse existing reducers as combiners?

A: Yes
B: No
C: Because the sum operation is both associative and commutative and the input and output types to the reduce method match
D: Because the sum operation in the Reducer is incompatible with the operation of a combiner
E: Because the combiner is incompatible with a Mapper, which doesn't use the same data type for both the key and value
F: Insufficient information

Assuming the following Hive statements execute successfully, choose the correct statements that describe the result:

from fooddata select context_ngrams(sentences(lines),
array("twiggy", "romato", null), 68);

A. A bigram of the top 68 sentences that contain the substring "twiggy romato" in the lines column of the input data A1 table.
B. An 68-value ngram of sentences that contain the words "twiggy" or "romato" in the lines column of the fooddata table.
C. A trigram of the top 68 sentences that contain "twiggy romato" followed by a null space in the lines column of the fooddata table.
D. A frequency distribution of the top 68 words that follow the subsequence "twiggy romato" in the lines column of the fooddata table.

Consider the following two relations, P and Q:

What is the output of the following Pig command?

Q = GROUP P BY p2;
DUMP Q;