exists
On this page
Definition
existsThe
existsoperator 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.existsis 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 } 7 } 8 }
Examples
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 }
The fruit collection has an Atlas Search index on the description
field that uses the standard analyzer.
The standard analyzer lower-cases all words and disregards common
stop words ("the", "a", "and", etc).
Basic Example
The following example searches for documents which include a field
called 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.
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 ])
The above query returns the following result:
1 { 2 "_id" : 4, 3 "description" : "Types of citrus fruit include lemons, oranges, and grapefruit.", 4 "quantities" : { 5 "lemons": 200, 6 "oranges": 240, 7 "grapefruit": 160 8 } 9 }
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 ])
The above query returns the following results:
1 { 2 "_id" : 1, 3 "type" : "apple", 4 "description" : "Apples come in several varieties, including Fuji, Granny Smith, and Honeycrisp." 5 } 6 { 7 "_id" : 3, 8 "type" : "apple", 9 "description" : "Apple pie and apple cobbler are popular apple-based desserts." 10 }
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.