CODEWITHSUNDEEP
elasticsearch
Stephen
Stephen

Reputation: 319

How do index aliases work in Elasticsearch?

I'm wondering how exactly do index aliases work behind the scenes in Elasticsearch?

Does an alias have a separate copy of the data for each index it is linked to? Or is it only aware of the index names, and the not the data within each index?

If this is the case, are aggregations much slower when performed on an alias with many linked indices?

Upvotes: 1

Views: 8845

Answers (1)

Paige Cook
Paige Cook

Reputation: 22555

From the Index Aliases Elasticsearch reference:

APIs in elasticsearch accept an index name when working against a specific index, and several indices when applicable. The index aliases API allow to alias an index with a name, with all APIs automatically converting the alias name to the actual index name. An alias can also be mapped to more than one index, and when specifying it, the alias will automatically expand to the aliases indices. An alias can also be associated with a filter that will automatically be applied when searching, and routing values.

So based on this it is only aware of the index names and not the data within each index. An aggregation could be slower when performed against an alias that spans multiple indexes. Because as far as I know in order to perform the aggregation action, Elasticsearch must collect the dataset to perform the aggregation function(s) against.

Upvotes: 3

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