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Query Reference

Operators & Collectors

Operators & Collectors

`wildcard` Operator

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, 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.	yes
`allowAnalyzedField`	boolean	Set to `true` if you run your query against a field indexed with a tokenizing analyzer. This avoids the field's analyzer from splitting the indexed value into many terms. Fields indexed with the Keyword Analyzer don't require this option.	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 isn't analyzed. Use the wildcard operator on fields indexed with tokenizing analyzers by setting allowAnalyzedField to true. Fields indexed with the Keyword Analyzer already treat the field value as a single term, so allowAnalyzedField: true isn't required.

If you use wildcard with allowAnalyzedField: true, MongoDB Search applies character filters and token filters based on the specified analyzer or custom analyzer for the field. MongoDB Search skips the tokenization and the output is always a single token.

The following examples show how the wildcard operator behaves when performing a search on analyzed fields:

Example

Standard Analyzer

Suppose that a field foo bar baz is indexed with the standard analyzer. MongoDB 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, MongoDB Search searches the field for any term that begins with foo bar but finds nothing, because no term exists.

Example

Keyword Analyzer

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:

"*\\\*"

Index Example

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 }

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 a MongoDB Search index on the movies collection and run the example queries on your cluster.

Interface

Query Examples

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

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

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

Back

vectorSearch

Query Path

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