wildcard
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Definition
wildcardThe
wildcardoperator enables queries which use special characters in the search string that can match any character.CharacterDescription?Matches any single character.*Matches 0 or more characters.\Escape character.wildcardis a term-level operator, meaning that thequeryfield is not analyzed. Term-level operators work well with the Keyword Analyzer, because thequeryfield is treated as a single term, with special characters included. For an example of querying against an analyzedqueryfield vs. a non-analyzedqueryfield, 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:
| 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.
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.
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.
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.
Use the following expression to escape a literal backslash:
"*\\\*"
➤ Use the Select your language drop-down menu to set the language of the examples on this page.
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.
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 $limit stage limits the results to 5 documents,
while the $project stage limits the results to only the title
field.
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.
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 $limit stage
limits the results to 5 documents, while the $project stage limits
the results to only the title field.
The above query returns the following results: