Question about segment merging


I am trying to understand the Definitive Guide and would appreciate if someone can help me out clarifying my thoughts.

I would like to ask two questions.

[1] In the book it says ,

Elasticsearch added a translog, or transaction log, which records every operation in Elasticsearch as it happens. With the translog, the process now looks like this:

In the segment merging process, is it first recorded in the translog and then data are flushed to the disk?

[2] If yes, is the number of operations and size of operation result for segment merging included in below section for Node Stats API ?

    "translog" : {
      "operations" : 9245364,
      "size_in_bytes" : 10886196986

Writing to the translog and segment merging are completely disconnected operations.

Every write operation is written to translog when it's received while segment merging is a different operation that works in the background.

The merging operations does not involves writting to translog. At most, it's all the way around.


Understood. Thank you.

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