exists
On this page
Definition
exists
The
exists
operator tests if a path to a specified indexed field name exists in a document. If the specified field exists but is not indexed, the document is not included with the result set.exists
is often used as part of a compound query in conjunction with other search clauses.
Syntax
exists
has the following syntax:
1 { 2 $search: { 3 "index": <index name>, // optional, defaults to "default" 4 "exists": { 5 "path": "<field-to-test-for>", 6 "score": <options> 7 } 8 } 9 }
Options
exists
uses the following terms to construct a query:
Field | Type | Description | Required? |
---|---|---|---|
path | string | Indexed field to search. | yes |
score | object | Score to assign to matching search results. To learn more
about the options to modify the default score, see
Score the Documents in the Results. | no |
Scoring Behavior
Atlas Search assigns a constant
score of 1
for all the
documents in the result set. You can customize the default Atlas Search score
using the score
options. To learn more about modifying the default
score returned by Atlas Search, see Modify the Score.
Examples
You can try the following examples in the Atlas Search Playground or your Atlas cluster.
Sample Collection
The examples on this page use a collection called fruit
that contains
the following documents:
1 { 2 "_id" : 1, 3 "type" : "apple", 4 "description" : "Apples come in several varieties, including Fuji, Granny Smith, and Honeycrisp." 5 }, 6 { 7 "_id" : 2, 8 "type" : "banana", 9 "description" : "Bananas are usually sold in bunches of five or six." 10 }, 11 { "_id" : 3, 12 "type": "apple", 13 "description" : "Apple pie and apple cobbler are popular apple-based desserts." 14 }, 15 { "_id" : 4, 16 "description" : "Types of citrus fruit include lemons, oranges, and grapefruit.", 17 "quantities" : { 18 "lemons": 200, 19 "oranges": 240, 20 "grapefruit": 160 21 } 22 }
Sample Index
The fruit
collection has a default dynamic Atlas Search index that uses the default
standard analyzer. The standard
analyzer lower-cases all words and disregards common stop words
("the", "a", "and",
etc).
Sample Queries
The following queries demonstrate the exists
operator in Atlas Search
queries.
Basic Example
The following example searches for documents which include a field
named type
.
1 db.fruit.aggregate([ 2 { 3 $search: { 4 "exists": { 5 "path": "type" 6 } 7 } 8 } 9 ])
The above query returns the first three documents of the collection.
The document with _id: 4
is not included because it does not have a
type
field.
➤ Try this in the Atlas Search Playground.
Embedded Example
Use dot notation to search for embedded fields. The following example
searches for documents which have a field named lemons
embedded
within a field named quantities
.
1 db.fruit.aggregate([ 2 { 3 "$search": { 4 "exists": { 5 "path": "quantities.lemons" 6 } 7 } 8 } 9 ])
➤ Try this in the Atlas Search Playground.
Compound Example
The following example uses exists
as part of a
compound query.
1 db.fruit.aggregate([ 2 { 3 $search: { 4 "compound": { 5 "must": [ 6 { 7 "exists": { 8 "path": "type" 9 } 10 }, 11 { 12 "text": { 13 "query": "apple", 14 "path": "type" 15 } 16 }], 17 "should": { 18 "text": { 19 "query": "fuji", 20 "path": "description" 21 } 22 } 23 } 24 } 25 } 26 ])
Both documents have a type
field, and both include the search term
apple
. The document with _id: 1
is returned first because it
satisfies the should
clause.
➤ Try this in the Atlas Search Playground.