index_prefixes

The index_prefixes parameter enables the indexing of term prefixes to speed up prefix searches. It accepts the following optional settings:

min_chars: The minimum prefix length to index. Must be greater than 0, and defaults to 2. The value is inclusive.
max_chars: The maximum prefix length to index. Must be less than 20, and defaults to 5. The value is inclusive.

This example creates a text field using the default prefix length settings:

  PUT my-index-000001 { "mappings": { "properties": { "body_text": { "type": "text", "index_prefixes": { } } } } }  

An empty settings object will use the default min_chars and max_chars settings

This example uses custom prefix length settings:

  PUT my-index-000001 { "mappings": { "properties": { "full_name": { "type": "text", "index_prefixes": { "min_chars" : 1, "max_chars" : 10 } } } } }  

index_prefixes parameter instructs Elasticsearch to create a subfield "._index_prefix". This field will be used to do fast prefix queries. When doing highlighting, add "._index_prefix" subfield to the matched_fields parameter to highlight the main field based on the found matches of the prefix field, like in the request below:

  GET my-index-000001/_search { "query": { "prefix": { "full_name": { "value": "ki" } } }, "highlight": { "fields": { "full_name": { "matched_fields": ["full_name._index_prefix"] } } } }  