how to switch on the elasticsearch stemming - elasticsearch

Question

I don't know how to turn on the Elasticsearch English word stemming. I am sorry I didn't find out a clear example to do that.
Here is what I did
Creating the index
PUT /staff/list/ -d
{
"settings" : {
"analysis": {
"analyzer": {
"standard": {
"type": "standard"
}
}
}
}
}
Adding document
PUT /staff/list/jason
{
"Title" : "searches"
}
when I search for search
GET /staff/list/_search?q=search
The result doesnt appear.
What index setting I should do to make the stemming works.
Many thanks in advance

Answer 1

Please note that the default Elasticsearch analyzer do not support stemming.
In order to support stemming you may need to create a custom analyzer.
Here is how you do it:
Create the index and define an analyzer called my_analyzer
PUT /staff
{
"settings" : {
"analysis": {
"filter": {
"filter_snowball_en": {
"type": "snowball",
"language": "English"
}
},
"analyzer": {
"my_analyzer": {
"filter": [
"lowercase",
"filter_snowball_en"
],
"type": "custom",
"tokenizer": "whitespace"
}
}
}
}
}
Configure mapping that assigns my_analyzer to list type
PUT /staff/_mapping/list
{
"list": {
"properties": {
"title": {
"type": "string",
"analyzer": "my_analyzer"
}
}
}
}
Index documents
PUT /staff/list/jason
{
"title": "searches"
}
PUT /staff/list/debby
{
"title": "searched open"
}
Search and stemmed results
GET staff/list/_search
{
"query": {
"query_string": {
"query": "title:opened"
}
}
}
Result
{
"took": 3,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 1,
"hits": [
{
"_index": "staff",
"_type": "list",
"_id": "debby",
"_score": 1,
"_source": {
"title": "open"
}
}]
}
}
As you can see in the search results, debby document which contains the term
open was returned although we where searching for opened.
Hope that helps.

Answer 2

When you create the index, you are doing nothing (just re-declaring the standard analyzer).
The standard analyzer is the default that Elasticsearch uses, which doesn't stem any word.
You need to map the fields to their respective analyzers at your index creation (mapping documentation):
PUT /staff -d
{
"mappings": {
"list": {
"properties": {
"Title": {
"type": "string",
"analyzer": "english"
}
}
}
}
}
I guess english analyzer fits to your case (which uses the standard tokenizer).