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wildcard

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  • Definition
  • Syntax
  • Options
  • Behavior
  • Examples

Definition

wildcard

The wildcard operator enables queries which use special characters in the search string that can match any character.

Character
Description
?
Matches any single character.
*
Matches 0 or more characters.
\
Escape character.

wildcard is a term-level operator, meaning that the query field is not analyzed. Term-level operators work well with the Keyword Analyzer, because the query field is treated as a single term, with special characters included. For an example of querying against an analyzed query field vs. a non-analyzed query field, see the analyzed field example.

Syntax

wildcard has the following syntax:

{
  $search: {
    "index": <index name>, // optional, defaults to "default"
    "wildcard": {
      "query": "<search-string>",
      "path": "<field-to-search>",
      "allowAnalyzedField": <boolean>,
      "score": <options>
    }
  }
}

Options

wildcard uses the following terms to construct a query:

Field
Type
Description
Necessity
Default
query
string or array of strings
String or strings to search for.
yes
path
string or array of strings
Indexed field or fields to search. You can also specify a wildcard path to search. See path construction for more information.
yes
allowAnalyzedField
boolean
Must be set to true if the query is run against an analyzed field.
no
false
score
object

Modify the score assigned to matching search term results. Options are:

  • boost: multiply the result score by the given number.

  • constant: replace the result score with the given number.

  • function: replace the result score using the given expression.

For information on using score in your query, see Score the Documents in the Results.

no

Behavior

wildcard is a term-level operator, meaning that the query field is not analyzed. It is possible to use the wildcard operator to perform searches on a field analyzed during indexing by setting the allowAnalyzedField option to true, but results will reflect that the query text is not analyzed.

Example

Suppose that a field foo bar baz is indexed with the standard analyzer. Atlas Search analyzes and indexes the field as foo, bar and baz. Searching for foo bar* on this field finds nothing, because the wildcard operator treats foo bar* as a single search term with a wildcard at the end. In other words, Atlas Search searches the field for any term that begins with foo bar but finds nothing, because no term exists.

Example

Searching for *Star Trek* on a field indexed with the keyword analyzer finds all documents in which the field contains the string Star Trek in any context. Searching for *Star Trek* on a field indexed with the standard analyzer finds nothing, because there is a space between Star and Trek, and the index contains no spaces.

Escape Character Behavior

When using the escape character in mongosh or with a driver, you must use a double backslash before the character to be escaped.

Example

To create a wildcard expression which searches for any string containing a literal asterisk in an aggregation pipeline, use the following expression:

"*\\**"

The first and last asterisks act as wildcards which match any characters, and the \\* matches a literal asterisk.

Note

Use the following expression to escape a literal backslash:

"*\\\*"

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Examples

The following examples use the movies collection in the sample_mflix database with a custom index definition that uses the keyword analyzer. If you have the sample dataset on your cluster, you can create an Atlas Search index on the movies collection and run the example queries on your cluster.

Tip

If you've already loaded the sample dataset, follow the Get Started with Atlas Search tutorial to create an index definition and run Atlas Search queries.

Index Definition

The following index definition indexes the title field in the movies collection with the keyword analyzer:

1{
2  "mappings": {
3    "fields": {
4      "title": {
5        "analyzer": "lucene.keyword",
6        "type": "string"
7      }
8    }
9  }
10}

The following example searches all title fields for movie titles that begin with Green D, followed by any number of other characters.

The above query returns the following results:

The following example searches all title fields for movie titles that begin with the string Wom?n (where ? may be any single character), followed by a space and then any number of additional characters.

The above query returns the following results:

Escape Character Example

The following example searches for documents in which the title field ends with a question mark.

Note

The following example is intended to run in mongosh. For more information about using the escape characters with a driver, see Escape Character Behavior.

The * character in the query field matches any characters, and the \\? string matches a literal question mark.

The above query returns the following results:

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