Should I force merge after resetting refresh interval after indexing

Elastic Stack Elasticsearch
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I am doing bulk indexing and as an optimization I set the refresh_interval of the indices to -1. I am going to set it back to the default after I am done. In one of the ES documents (perhaps old) I read I have to forcemerge. I don't see a need for it based on what I read about refresh_interval, should I?

Thanks

2

You don't have to do it at all. You can do it, but you only should do it, if you do not have any further writes on that index - otherwise merges will happen anyway again over time.

See https://www.elastic.co/guide/en/elasticsearch/reference/6.3/tune-for-search-speed.html#_force_merge_read_only_indices

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Mine is a time based index and after last write there aren't any writes. I didn't do force merge but just index refresh. I see possibly the last line I inserted (at least last line in my log feed) from the search. I say 'possibly' as there are other hits with search but the last one did show up. The index is large (about 1.6 TB) so don't want to force merge if I can get away not doing it.

So are you sure I have to force merge to see the results of insertion or are you saying it helps (usage of 'should' in your answer is confusing)?

I understand force merge makes searches faster/better on read only indices but that optimization is for another day.

Thanks for the reponse
S

4

A refresh is perfectly fine to see the latest changes. You might want to run a flush, so that everything is persisted to disk, so recovery is going to be faster., in case it is needed.

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