Elasticsearch match with stemming - search

Question

How do I do a search for a stemmed match?
I.e. at the moment I have many documents that contain the word "skateboard" in the item_title field, but only 3 documents that contain the word "skateboards". Because of this, when I do the following search:
POST /my_index/my_type/_search
{
"size": 100,
"query" : {
"multi_match": {
"query": "skateboards",
"fields": [ "item_title^3" ]
}
}
}
I only get 3 results. However, I would like also documents with the word "skateboard" to be returned.
From what I understand from Elasticsearch I would expect that this is done by specifying a mapping on the item_title field that contains an analyser which indexes the stemmed version of each word, but I can't seem to find the documentation on how to do this, which suggests that it's done in a different way.
Suggestions?

Answer 1

Here's one example:
PUT /stem
{
"settings": {
"analysis": {
"filter": {
"filter_stemmer": {
"type": "stemmer",
"language": "english"
}
},
"analyzer": {
"tags_analyzer": {
"type": "custom",
"filter": [
"standard",
"lowercase",
"filter_stemmer"
],
"tokenizer": "standard"
}
}
}
},
"mappings": {
"test": {
"properties": {
"item_title": {
"analyzer": "tags_analyzer",
"type": "text"
}
}
}
}
}
Index some sample docs:
POST /stem/test/1
{
"item_title": "skateboards"
}
POST /stem/test/2
{
"item_title": "skateboard"
}
POST /stem/test/3
{
"item_title": "skate"
}
Perform the query:
GET /stem/test/_search
{
"query": {
"multi_match": {
"query": "skateboards",
"fields": [
"item_title^3"
]
}
},
"fielddata_fields": [
"item_title"
]
}
And see the results:
"hits": [
{
"_index": "stem",
"_type": "test",
"_id": "1",
"_score": 1,
"_source": {
"item_title": "skateboards"
},
"fields": {
"item_title": [
"skateboard"
]
}
},
{
"_index": "stem",
"_type": "test",
"_id": "2",
"_score": 1,
"_source": {
"item_title": "skateboard"
},
"fields": {
"item_title": [
"skateboard"
]
}
}
]
I have added, also, the fielddata_fields element so that you can see how the content of the field has been indexed. As you can see, in both cases, the indexed term is skateboard.