MongoDB Atlas Search not showing results when typing few characters - mongodb

Question

The problem I am facing is that I want to develop an autocomplete search bar using Mean Stack like the one in this site, but when I type, for example, 'ag' it's not returning the right location that should be 'Aguascalientes'.
I have two different search indexes set up and a different query for each.
First Index:
{
"mappings": {
"dynamic": false,
"fields": {
"name": {
"foldDiacritics": false,
"maxGrams": 7,
"minGrams": 3,
"tokenization": "edgeGram",
"type": "autocomplete"
},
"searchName": {
"foldDiacritics": false,
"maxGrams": 7,
"minGrams": 3,
"tokenization": "edgeGram",
"type": "autocomplete"
}
}
}
}
First Query:
[
{
$search: {
index: "autocomplete2",
compound: {
must: [
{
text: {
query: search,
path: "searchName",
fuzzy: {
maxEdits: 2,
},
},
},
],
},
},
},
{
$limit: 10,
},
]
The first ones are not returning any document at all. But the second example is:
{
"mappings": {
"dynamic": false,
"fields": {
"name": {
"analyzer": "lucene.standard",
"type": "string"
},
"searchName": {
"analyzer": "lucene.standard",
"type": "string"
}
}
}
}
Query:
[
{
$search: {
index: 'default',
compound: {
must: [
{
text: {
query: search,
path: 'name',
fuzzy: {
maxEdits: 1,
},
},
},
{
text: {
query: search,
path: 'searchName',
fuzzy: {
maxEdits: 1,
},
},
},
],
},
},
},
{
$limit: 5,
},
]
The second example is only returning documents if the search term 'aguascalient' but is not returning any document if the search term is shorter like the site. Maybe it has something to do with the fuzzy edits but if I set it up to greater than 2 I get an error.
Also the order is not right, it returns first the CITY and second the STATE but I need the STATE first because the search term is more similar than the city. Let me explain, search field for STATE is only 'Aguascalientes' but search field cities is 'Aguascalientes Aguascalientes' so I don't know why is not working properly. Maybe in that case I should give weights accordingly but I'm not sure if it's the right approach to solve this.
My data structure:
{
"_id": "638d0ffc34ad076c6bd12cb6",
"depth": 2,
"label": "CITY",
"location_id": "V1-C-247",
"name": "Aguascalientes",
"parent": "Aguascalientes",
"fullName": "Aguascalientes, Aguascalientes",
"parentId": "V1-B-61",
"searchName": "Aguascalientes Aguascalientes",
}
{
"_id": "638d0ffc34ad076c6bd12cb6",
"depth": 1,
"label": "STATE",
"location_id": "V1-C-248",
"name": "Aguascalientes",
"parent": null,
"fullName": "Aguascalientes",
"parentId": null,
"searchName": "Aguascalientes",
}

Answer 1

For the first index + query setup:
First, you are indexing the name field but are not searching on it. I will remove it from the code snippets for readability, but you can add it back to your index definition if you find you need to search on it.
There are two problems with the this index + query setup if you want to return results with a query for "ag". You have searchName defined as a field mapping of type autocomplete, but you also need to use the autocomplete operator in your query:
[
{
$search: {
index: "autocomplete2",
compound: {
must: [
{
autocomplete: {
query: search,
path: "searchName",
},
},
],
},
},
},
{
$limit: 10,
},
]
Second, in your index definition field mapping for searchName, you have minGram set to 3 and maxGram set to 7. Based on the documentation for the autocomplete field mapping, this means that your data will be tokenized into sequences of character lengths between 3 to 7, using the selected tokenization strategy. Since you have selected edgeGram, the tokens generated by the text "Aguascalientes" will be tokenized starting from the left edge, resulting in tokens "agu", "agua", "aguas", "aguasc", "aguasca". Since the search term "ag" does not match any of the tokens, nothing is returned. So, you must change the minGram to 2 to get the token "ag":
{
"mappings": {
"dynamic": false,
"fields": {
"searchName": {
"foldDiacritics": false,
"maxGrams": 7,
"minGrams": 2,
"tokenization": "edgeGram",
"type": "autocomplete"
}
}
}
}
Finally, if you want the document with an exact match to return over a partial match, ie. "Aguascalientes" should return before "Aguascalientes Aguascalientes", you need to implement exact matching. Here is a MongoDB blog post outlining a few options.
One option that I tried: In the index, use a keyword analyzer on the "searchName" field typed as a string data type. In the query, use the text operator nested in a should clause so that exact matches will return higher than other results.
Index:
{
"mappings": {
"dynamic": false,
"fields": {
"searchName": [
{
"foldDiacritics": false,
"maxGrams": 7,
"type": "autocomplete"
},
{
"analyzer": "lucene.keyword",
"searchAnalyzer": "lucene.keyword",
"type": "string"
}
]
}
}
}
Query:
[
{
$search: {
compound: {
must: [
{
autocomplete: {
query: search,
path: "searchName"
}
}
],
should:[
{
text: {
query: search,
path: "searchName"
}
}
],
},
},
},
]