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_tier field

When performing queries across multiple indexes, it is sometimes desirable to target indexes held on nodes of a given data tier (data_hot, data_warm, data_cold or data_frozen). The _tier field allows matching on the tier_preference setting of the index a document was indexed into. The preferred value is accessible in certain queries :

 PUT index_1/_doc/1 { "text": "Document in index 1" } PUT index_2/_doc/2?refresh=true { "text": "Document in index 2" } GET index_1,index_2/_search { "query": { "terms": { "_tier": ["data_hot", "data_warm"] } } }
  1. Querying on the _tier field

Typically a query will use a terms query to list the tiers of interest but you can use the _tier field in any query that is rewritten to a term query, such as the match, query_string, term, terms, or simple_query_string query, as well as prefix and wildcard queries. However, it does not support regexp and fuzzy queries.

The tier_preference setting of the index is a comma-delimited list of tier names in order of preference i.e. the preferred tier for hosting an index is listed first followed by potentially many fall-back options. Query matching only considers the first preference (the first value of a list).