ElasticSearch autocomplete doesn't work with the middle words - elasticsearch

Question

Using python elasticsearch-dsl:
class Record(Document):
tags = Keyword()
tags_suggest = Completion(preserve_position_increments=False)
def clean(self):
self.tags_suggest = {
"input": self.tags
}
class Index:
name = 'my-index'
settings = {
"number_of_shards": 2,
}
When I index
r1 = Record(tags=['my favourite tag', 'my hated tag'])
r2 = Record(tags=['my good tag', 'my bad tag'])
And when I try to use autocomplete with the word in the middle:
dsl = Record.search()
dsl = dsl.suggest("auto_complete", "favo", completion={"field": "tags_suggest"})
search_response = dsl.execute()
for option in search_response.suggest.auto_complete[0].options:
print(option.to_dict())
It won't return anything, but it will when I search "my favo". Any good practices to fix that (make it return 'my favourite tag' when I request suggestions for "favo")?

Answer 1

Check Mapping
Search in Elasticsearch, Is also depends on how you are indexing your data. I would suggest to have look on index mapping with the below query:
curl -X GET "elasticsearch.url:port/index_name/_mapping?pretty"
You need to check how data is being inserted like is it using any analyzer or tokeninzer to save data. If you have not specified any analyzer elasticsearch default uses standard analyzer. It will produce the terms accordingly.
As per your use case you need to apply analyzer, tokens & filters. Here is the one Example where i have to use like query and implemented ngram token filter.
Solution
As i can see you are using suggester, The suggest feature suggests similar looking terms based on a provided text by using a suggester.
If you want to achieve autocomplete, I would suggest to use search as you type.
I tried to reproduce your use case and below is something which worked for me.
Create Index
PUT /test1?pretty
{
"mappings": {
"properties": {
"tags": {
"type": "search_as_you_type"
}
}
}
}
Indexing data
POST test1/_doc?pretty
{
"tags":"my favourite tag"
}
POST test1/_doc?pretty
{
"tags":"my hated tag"
}
POST test1/_doc?pretty
{
"tags":"my good tag"
}
POST test1/_doc?pretty
{
"tags":"my bad tag"
}
Query with your keyword
GET /test1/_search?pretty
{
"query": {
"multi_match": {
"query": "my",
"type": "bool_prefix",
"fields": [
"tags",
"tags._2gram",
"tags._3gram"
]
}
}
}
GET /test1/_search?pretty
{
"query": {
"multi_match": {
"query": "bad",
"type": "bool_prefix",
"fields": [
"tags",
"tags._2gram",
"tags._3gram"
]
}
}
}
GET /test1/_search?pretty
{
"query": {
"multi_match": {
"query": "fav",
"type": "bool_prefix",
"fields": [
"tags",
"tags._2gram",
"tags._3gram"
]
}
}
}

Answer 2

You can achive this by setting preserve_position_increments parameter to false in your mappings.
"tags_completion": {
"type": "completion",
"analyzer": "simple",
"preserve_separators": false,
"preserve_position_increments": false,
"max_input_length": 50
}
You can query it in console like this:
GET /_search
{
"suggest" : {
"my-suggester": {
"prefix": "favou",
"completion": {
"field": "tags_completion",
"skip_duplicates": true,
"fuzzy": {
"fuzziness": 1
}
}
}
}
}
}