exists

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:

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{
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  $search: {
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    "index": <index name>, // optional, defaults to "default"
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    "exists": {
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      "path": "<field-to-test-for>",
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      "score": <options>
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    }
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  }
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}

Options

exists uses the following terms to construct a query:

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

The examples on this page use a collection called fruit that contains the following documents:

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{
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  "_id" : 1,
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  "type" : "apple",
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  "description" : "Apples come in several varieties, including Fuji, Granny Smith, and Honeycrisp."
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},
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{
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  "_id" : 2,
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  "type" : "banana",
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  "description" : "Bananas are usually sold in bunches of five or six."
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},
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{ "_id" : 3,
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  "type": "apple",
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  "description" : "Apple pie and apple cobbler are popular apple-based desserts."
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},
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{ "_id" : 4,
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  "description" : "Types of citrus fruit include lemons, oranges, and grapefruit.",
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  "quantities" : {
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    "lemons": 200,
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    "oranges": 240,
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    "grapefruit": 160
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  }
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}

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).

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db.fruit.aggregate([
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  {
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    $search: {
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      "exists": {
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        "path": "type"
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      }
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    }
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  }
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])

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db.fruit.aggregate([
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  {
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    $search: {
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      "exists": {
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        "path": "quantities.lemons"
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      }
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    }
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  }
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])

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{
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  "_id" : 4,
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  "description" : "Types of citrus fruit include lemons, oranges, and grapefruit.",
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  "quantities" : {
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    "lemons": 200,
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    "oranges": 240,
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    "grapefruit": 160
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  }
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}

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db.fruit.aggregate([
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  {
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    $search: {
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      "compound": {
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        "must": [
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          {
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            "exists": {
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              "path": "type"
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            }
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          },
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          {
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            "text": {
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              "query": "apple",
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              "path": "type"
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            }
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          }],
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        "should": {
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          "text": {
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            "query": "fuji",
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            "path": "description"
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          }
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        }
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      }
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    }
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  }
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])

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{
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  "_id" : 1,
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  "type" : "apple",
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  "description" : "Apples come in several varieties, including Fuji, Granny Smith, and Honeycrisp."
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}
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{
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  "_id" : 3,
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  "type" : "apple",
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  "description" : "Apple pie and apple cobbler are popular apple-based desserts."
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}