Atlas Search works too slow when using facet - mongodb

Question

I have a big collection (over 22M records, approx. 25GB) on an M10 cluster with MongoDB version 4.4.10. I set up an Atlas search index on one field (address) and it works pretty fast when I request through the search tester. However, when I try to paginate it by specifying a facet, it gets extremely slow in comparison with the query without the facet. Is there a way to optimize the facet or somehow replace the facet with one that works faster ? Below are the plain query and another one with the facet:
db.getCollection("users").aggregate([{
$search: {
index: 'address',
text: {
query: '7148 BIG WOODS DR',
path: {
'wildcard': '*'
}
}
}
}]);
db.getCollection("users").aggregate([{
$search: {
index: 'address',
text: {
query: '7148 BIG WOODS DR',
path: {
'wildcard': '*'
}
}
}
}, {
$facet: {
paginatedResult: [
{
$limit: 50
},
{
$skip: 0
}
],
totalCount: [
{
$count: 'total'
}
]
}
}]);

Answer 1

The fast and recommend way is using facet with the $searchMeta stage to retrieve metadata results only for the query
"$searchMeta": {
"index":"search_index_with_facet_fields",
"facet":{
"operator":{
"compound":{
"must":[
{
"text":{
"query":"red shirt",
"path":{
"wildcard":"*"
}
}
},
{
"compound":{
"filter":[
{
"text":{
"query":["clothes"],
"path":"category"
}
},
{
"text":{
"query":[
"maroon",
"blackandred",
"blackred",
"crimson",
"burgandy",
"burgundy"
],
"path":"color"
}
}
]
}
}
]
}
},
"facets":{
"brand":{
"type":"string",
"path":"brand"
},
"size":{
"type":"string",
"path":"size"
},
"color":{
"type":"string",
"path":"color"
}
}
}
}
}
Here we are fetching 3 facets brand, size, and color, which we need to be defined in your search_index as Facet fields such as
{
"mappings": {
"dynamic": false,
"fields": {
"category": [
{
"type": "string"
}
],
"brand": [
{
"type": "string"
},
{
"type": "stringFacet"
}
],
"size": [
{
"type": "string"
},
{
"type": "stringFacet"
}
],
"color": [
{
"type": "string"
},
{
"type": "stringFacet"
}
]
}
}
}
category is defined only as string since we are not using it in facets but only as a filter field.
We can also replace filter op with must or should based on our requirement.
Finally, we will get as our result.
*p.s. I am also new to mongo and got to this solution after searching a lot, so please upvote if you find it useful, also let me know if there is any error/improvement you notice. Thanks *