SqlUserDefinedCombiner(Mode=CombinerMode.Inner)

Understanding SqlUserDefinedCombiner in Combiner Mode

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Question

Combiner mode attempts to distribute huge skewed-key value sets to several vertices that support concurrent execution of the work.

There are various attributes of combiner mode? What is the meaning of SqlUserDefinedCombiner(Mode=CombinerMode.Inner).

Answers

A. Every output row potentially depends upon all the input rows from left and right with the same key value.

B. Every output row depends upon a single input row from the left (and potentially all rows with the same key value from the right).

C. Every output row depends upon a single input row from the right (and potentially all rows with the same key value from the left).

D. Every output row depends upon a single input row from the left and the right with the same value.

E. None of these.

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Explanations

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A. B. C. D. E.

Correct Answer: D

The following are the attributes of the combiner mode:

‘SqlUserDefinedCombiner(Mode=CombinerMode Full): Every output row potentially depends on all the input rows from left and
right with the same key value.

‘SqlUserDefinedCombiner(Mode=CombinerMode.Left): Every output row depends on a single input row from the left (and
potentially all rows from the right with the same key value).

qlUserDefinedCombiner(Mode=CombinerMode.Right): Every output row depends on a single input row from the right (and
potentially all rows from the left with the same key value).

‘SqlUserDefinedCombiner(Mode=CombinerMode.Inner): Every output row depends on a single input row from the left and the
right with the same value.

Option A is incorrect.

This is the description for SqlUserDefinedCombiner(Mode=CombinerMode.Full).

Option B is incorrect.

This is the description for SqlUserDefinedCombiner(Mode=CombinerMode.Left).

Option C is incorrect.

This is the description for SqlUserDefinedCombiner(Mode=CombinerMode.Right).

Option D is correct.

This is the description for SqlUserDefinedCombiner(Mode=CombinerMode.Inner).

Option E is incorrect.

D is the right answer.

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Combiner mode is a feature in distributed computing where the processing of data is divided among several vertices or nodes in a cluster. Combiner mode aims to optimize the processing of huge skewed-key value sets by distributing them to multiple vertices, which can work concurrently. This helps in reducing the processing time and improves the overall efficiency of the system.

In the context of SqlUserDefinedCombiner(Mode=CombinerMode.Inner), the mode 'Inner' specifies that the combiner will be executed after the mapper but before the reducer. This means that the combiner will receive the data from the mapper, perform its computation, and then pass the output to the reducer for further processing. The combiner is responsible for aggregating and reducing the data at each vertex before passing it to the reducer.

Option B states that every output row depends upon a single input row from the left (and potentially all rows with the same key value from the right). This option describes the behavior of a join operation, where every row in the output is dependent on a single row from the left table and potentially all the rows with the same key value from the right table. Hence, this option is not related to the behavior of SqlUserDefinedCombiner with CombinerMode.Inner.

Option C describes a similar behavior as option B but with the roles of the tables reversed. Hence, this option is also not related to the behavior of SqlUserDefinedCombiner with CombinerMode.Inner.

Option D states that every output row depends upon a single input row from the left and the right with the same value. This option describes the behavior of an inner join, where every output row depends on a single input row from both tables with the same key value. This option is also not related to the behavior of SqlUserDefinedCombiner with CombinerMode.Inner.

Option A states that every output row potentially depends upon all the input rows from left and right with the same key value. This option describes the behavior of a full outer join, where every output row is dependent on all the rows from both tables with the same key value. This option is also not related to the behavior of SqlUserDefinedCombiner with CombinerMode.Inner.

Hence, the correct answer is E. None of these options describes the behavior of SqlUserDefinedCombiner with CombinerMode.Inner.

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