Update vs Reindex

Elastic Stack Elasticsearch
1

Hello,

I am evaluating a few ways of organizing my indices. One of the questions I had was generally speaking, what is the difference in overhead(if any) between updating a document within an index vs using the reindex API to move a document from one index to another? Is there a difference at all behind the scenes in terms of one approach being able to scale better? Thanks!

2

Assuming you don't delete the reindexed document, it's a lower cost operation.

3

Thanks for the reply. To clarify, are you saying that reindex is a lower cost operation than an update?

4

Yes.
An update is a reindex of the original document, then marking that original as deleted, then having to merge it out of the segement.

A reindex adds the original document to a new segment in a new index (usually), and leaves the original.

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5

If I happened to delete the original document after reindexing, it would be approximately the same cost as an update behind the scenes?

6

Ultimately, yes.

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