Count Search Results
Atlas Search facet and count are in preview, but can be used in production applications. If there are any syntax or behavior changes between the preview stage and general availability (GA), we will proactively communicate before introducing any breaking changes. The MongoDB Cloud Support team will help troubleshoot any issues related to using this feature as part of your contract.
The Atlas Search count option adds a field to the metadata results document that displays a count of the search
results for the query. You can use count to determine the size of
the result set. You can use it in the $search
or $searchMeta stage. You must use it in conjuction with
the operators or collectors to display either the total number of documents or a
lower bound on the number of documents that match the query.
MongoDB recommends using count with the $searchMeta
stage to retrieve metadata results only for the query. To retrieve
metadata results and query results using the $search stage,
you must use the $$SEARCH_META variable. To learn more, see
SEARCH_META Aggregation Variable.
Atlas Search doesn't include the count results in the results for
queries run with count in explain mode.
Syntax
count has the following syntax:
{ "$searchMeta"|"$search": { "index": "<index name>", // optional, defaults to "default" "<operator>": { <operator-specifications> }, "count": { "type": "lowerBound"|"total", "threshold": <number-of-documents> //optional } } }
Options
Field | Type | Description | Required? |
|---|---|---|---|
type | int | Type of count of the documents in the result set. Value can be one of the following:
If omitted, defaults to | no |
threshold | int | Number of documents to include in the exact count if type is
lowerBound. If omitted, defaults to 1000, which
indicates that any number up to 1000 is an exact count and
any number above 1000 is a rough count of the number of
documents in the result. | no |
Count Results
The count document included in the results document contains the following integer fields:
SEARCH_META Aggregation Variable
When you run your query using the $search stage, Atlas Search
stores the metadata results in the $$SEARCH_META variable and
returns only the search results. You can use the $$SEARCH_META
variable in all the supported aggregation pipeline stages to view the metadata
results for your $search query.
You can't use the $$SEARCH_META variable to retrieve metadata
results for queries over sharded collections.
MongoDB recommends using the $$SEARCH_META variable only if you
need both the search results and the metadata results. Otherwise, use
the:
$searchstage for just the search results.$searchMetastage for just the metadata results.
Suppose an index on the released field in the
sample_mflix.movies collection:
{ "mappings": { "dynamic": false, "fields": { "released": { "type": "date" } } } }
The following query searches for movies released near September
01, 2011 in the movies collection. The query requests a total
count of the results. The query includes a:
$projectstage to exclude all fields excepttitleandreleasedfrom the documents and to include the metadata results stored in the$$SEARCH_METAvariable as the value of a field namedmeta.$limitstage to limit the output to2documents.
db.movies.aggregate([ { "$search": { "near": { "path": "released", "origin": ISODate("2011-09-01T00:00:00.000+00:00"), "pivot": 7776000000 }, "count": { "type": "total" } } }, { $project: { "meta": "$$SEARCH_META", "title": 1, "released": 1 } }, { "$limit": 2 } ])
Atlas Search returns the following results for the query:
{ "_id" : ObjectId("573a13c3f29313caabd6b025"), "title" : "Submarino", "released" : ISODate("2011-09-01T00:00:00Z"), "meta" : { "count" : { "total" : NumberLong(23026) } } } { "_id" : ObjectId("573a13c7f29313caabd748f7"), "title" : "Devil's Playground", "released" : ISODate("2011-09-01T00:00:00Z"), "meta" : { "count" : { "total" : NumberLong(23026) } } }
To learn more about the results, see Count Results.
Examples
The following example uses an index on the year field in the
sample_mflix.movies collection:
{ "mappings": { "dynamic": false, "fields": { "year": { "type": "number" } } } }