Elasticsearch: how to write the mapping for a multi-valued field?

Question

I am new to Elasticsearch. Forgive me if this is obvious. Googled it but did not find how to write the mapping for a mutlivalued field (strings). I only found how to write a multivalued document and search on a multivalued field: http://www.elasticsearch.org/guide/en/elasticsearch/guide/current/_multi_value_fields_2.html

Thanks for any help!

Answer 1

A multivalued field is different from Elastic's multi_field. It is described here:

https://www.elastic.co/guide/en/elasticsearch/reference/0.90/mapping-multi-field-type.html

Current documentation mentions multi-fields here: https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping.html#_field_datatypes

A multivalued field as I understand it (and I think that is what you meant by it, as well) is one that contains several values that will be searched separately from each other:

Example:

Field color, multivalued, keyword containing the following values: "black", "blue", "white". When the query contains "white", there will be a match. The score will be different then if you have a whitespace delimited field with three tokens "black blue white" where white comes last.

In Elasticsearch, there is no dedicated array type. Any field can contain zero or more values by default, however, all values in the array must be of the same datatype. (https://www.elastic.co/guide/en/elasticsearch/reference/current/array.html)

Elastic just adds values implicitly to fields. There won't be any error handling like in SOLR with an explicit multiValued=false. You will have to check during import time if you want to make sure a field is not containing a list of values.

If one or more documents have multiple values for a certain field, this field's values are displayed as array in the JSON results no matter how many values there are for a specific document. So the result type of that field is consistent across the index but it is not reflected in the mapping.