How can I get auto-suggestions for synonyms match in elasticsearch - elasticsearch

Question

I'm using the code below and it does not give auto-suggestion as curd when i type "cu"
But it does match the document with yogurt which is correct.
How can I get both auto-complete for synonym words and document match for the same?
PUT products
{
"settings": {
"index": {
"analysis": {
"analyzer": {
"synonym_analyzer": {
"tokenizer": "standard",
"filter": [
"lowercase",
"synonym_graph"
]
}
},
"filter": {
"synonym_graph": {
"type": "synonym_graph",
"synonyms": [
"yogurt, curd, dahi"
]
}
}
}
}
}
}
PUT products/_mapping
{
"properties": {
"description": {
"type": "text",
"analyzer": "synonym_analyzer"
}
}
}
POST products/_doc
{
"description": "yogurt"
}
GET products/_search
{
"query": {
"match": {
"description": "cu"
}
}
}

Answer 1

When you provide a list of synonyms in a synonym_graph filter it simply means that ES will treat any of the synonyms interchangeably. But when they're analyzed via the standard analyzer, only full-word tokens will be produced:
POST products/_analyze?filter_path=tokens.token
{
"text": "yogurt",
"field": "description"
}
yielding:
{
"tokens" : [
{
"token" : "curd"
},
{
"token" : "dahi"
},
{
"token" : "yogurt"
}
]
}
As such, a regular match_query won't cut it here because the standard analyzer hasn't provided it with enough context in terms of matchable substrings (n-grams).
In the meantime you can replace match with match_phrase_prefix which does exactly what you're after -- match an ordered sequence of characters while taking into account the synonyms:
GET products/_search
{
"query": {
"match_phrase_prefix": {
"description": "cu"
}
}
}
But that, as the query name suggests, is only going to work for prefixes. If you fancy an autocomplete that suggests terms regardless of where the substring matches occur, have a look at my other answer where I talk about leveraging n-grams.