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As hinted in the previous chapter, there's a new kid on the block to support search-as-you-type use cases — a field data type aptly named
search_as_you_type.Let's explore it in the common context of multi-word autocomplete queries where the order of the terms does not matter.
Use Case
I'm building an autocomplete for my catalogue of medical articles. Each article has a
title:{ "id": 1, "title": "Complete Blood Count" }
{ "id": 2, "title": "Preventing Blood Clots" }
{ "id": 3, "title": "What Is the CEA Test?" }
{ "id": 4, "title": "Coughing up Blood" }
...When I search for the query
blood c, I want the docs #1, #2, and #4 to be suggested. #4 too despite the fact that the word blood is not directly followed by the letter c.On top of that, since some articles have duplicate titles, I want to only show unique titles in my autocomplete.
Approach
Let's set up an index where the title is a multi-field covering search_as_you_type to query on and keyword to aggregate on:
PUT articles
{
"mappings": {
"properties": {
"title": {
"type": "text",
"fields": {
"as_you_type": {
"type": "search_as_you_type"
},
"keyword": {
"type": "keyword"
}
}
}
}
}
}Let's then sync some medical articles' titles:
POST articles/_doc
{"title":"Complete Blood Count"}
POST articles/_doc
{"title":"Beyond COVID-19: Can mRNA Treat Diseases, Too?"}
POST articles/_doc
{"title":"Complete Blood Count"}
POST articles/_doc
{"title":"Preventing Blood Clots"}
POST articles/_doc
{"title":"What Is the CEA Test?"}
POST articles/_doc
{"title":"Coughing up Blood"}Now, assuming that people search for things in-order, we could start with a phrase_prefix query followed by a terms aggregation ordered by the max score of each individual term:
POST articles/_search
{
"size": 0,
"query": {
"match_phrase_prefix": {
"title": "blood c"
}
},
"aggs": {
"by_unique_titles": {
"terms": {
"field": "title.keyword",
"order": {
"max_score": "desc"
}
},
"aggs": {
"max_score": {
"max": {
"script": "_score"
}
}
}
}
}
}