$regexMatch (aggregation)

On this page本页内容

Definition定义

$regexMatch

New in version 4.2.版本4.2中的新功能。

Performs a regular expression (regex) pattern matching and returns:执行正则表达式（regex）模式匹配并返回：

  • true if a match exists.如果存在匹配项，则为true。
  • false if a match doesn’t exist.如果不存在匹配项，则为false。

MongoDB uses Perl compatible regular expressions (i.e. “PCRE” ) version 8.41 with UTF-8 support.MongoDB使用Perl兼容的正则表达式（即“PCRE”）版本8.41，支持UTF-8。

Prior to MongoDB 4.2, aggregation pipeline can only use the query operator $regex in the $match stage. For more information on using regex in a query, see $regex.有关在查询中使用regex的更多信息，请参阅$regex。

Syntax语法

The $regexMatch operator has the following syntax:语法如下所示：

{ $regexMatch: { input: <expression> , regex: <expression>, options: <expression> } }
Field字段Description描述
input

The string on which you wish to apply the regex pattern. Can be a string or any valid expression that resolves to a string.

regex

The regex pattern to apply. Can be any valid expression that resolves to either a string or regex pattern /<pattern>/. When using the regex /<pattern>/, you can also specify the regex options i and m (but not the s or x options):

  • "pattern"
  • /<pattern>/
  • /<pattern>/<options>

Alternatively, you can also specify the regex options with the options field. To specify the s or x options, you must use the options field.

You cannot specify options in both the regex and the options field.

options

Optional. The following <options> are available for use with regular expression.

Note

You cannot specify options in both the regex and the options field.不能同时在regex和options字段中指定选项。

Option选项Description描述
i Case insensitivity to match both upper and lower cases. 不区分大小写以匹配大小写。You can specify the option in the options field or as part of the regex field.可以在options字段中指定该选项，也可以将其作为正则表达式字段的一部分指定。
m

For patterns that include anchors (i.e. ^ for the start, $ for the end), match at the beginning or end of each line for strings with multiline values. Without this option, these anchors match at beginning or end of the string.

If the pattern contains no anchors or if the string value has no newline characters (e.g. \n), the m option has no effect.

x

“Extended” capability to ignore all white space characters in the pattern unless escaped or included in a character class.

Additionally, it ignores characters in-between and including an un-escaped hash/pound (#) character and the next new line, so that you may include comments in complicated patterns. This only applies to data characters; white space characters may never appear within special character sequences in a pattern.这仅适用于数据字符；空白字符可能永远不会出现在图案中的特殊字符序列中。

The x option does not affect the handling of the VT character (i.e. code 11).

You can specify the option only in the options field.

s

Allows the dot character (i.e. .) to match all characters including newline characters.

You can specify the option only in the options field.

Returns返回

The operator returns a boolean:运算符返回一个布尔值：

  • true if a match exists.
  • false if a match doesn’t exist.

See also参阅

Behavior行为

$regexMatch and Collation

$regexMatch ignores the collation specified for the collection, db.collection.aggregate(), and the index, if used.

For example, the create a sample collection with collation strength 1 (i.e. compare base character only and ignore other differences such as case and diacritics):

db.createCollection( "myColl", { collation: { locale: "fr", strength: 1 } } )

Insert the following documents:

db.myColl.insertMany([
   { _id: 1, category: "café" },
   { _id: 2, category: "cafe" },
   { _id: 3, category: "cafE" }
])

Using the collection’s collation, the following operation performs a case-insensitive and diacritic-insensitive match:使用集合的排序规则，以下操作执行不区分大小写和不区分重音的匹配：

db.myColl.aggregate( [ { $match: { category: "cafe" } } ] )

The operation returns the following 3 documents:

{ "_id" : 1, "category" : "café" }
{ "_id" : 2, "category" : "cafe" }
{ "_id" : 3, "category" : "cafE" }

However, the aggregation expression $regexMatch ignores collation; that is, the following regular expression pattern matching examples are case-sensitive and diacritic sensitive:

db.myColl.aggregate( [ { $addFields: { results: { $regexMatch: { input: "$category", regex: /cafe/ }  } } } ] )
db.myColl.aggregate(
   [ { $addFields: { results: { $regexMatch: { input: "$category", regex: /cafe/ }  } } } ],
   { collation: { locale: "fr", strength: 1 } }       // Ignored in the $regexMatch
)

Both operations return the following:

{ "_id" : 1, "category" : "café", "results" : false }
{ "_id" : 2, "category" : "cafe", "results" : true }
{ "_id" : 3, "category" : "cafE", "results" : false }

To perform a case-insensitive regex pattern matching, use the i Option instead. See i Option for an example.

Examples示例

$regexMatch and Its Options

To illustrate the behavior of the $regexMatch operator as discussed in this example, create a sample collection products with the following documents:

db.products.insertMany([
   { _id: 1, description: "Single LINE description." },
   { _id: 2, description: "First lines\nsecond line" },
   { _id: 3, description: "Many spaces before     line" },
   { _id: 4, description: "Multiple\nline descriptions" },
   { _id: 5, description: "anchors, links and hyperlinks" },
   { _id: 6, description: "métier work vocation" }
])

By default, $regexMatch performs a case-sensitive match. For example, the following aggregation performs a case-sensitive $regexMatch on the description field. The regex pattern /line/ does not specify any grouping:

db.products.aggregate([
   { $addFields: { result: { $regexMatch: { input: "$description", regex: /line/ } } } }
])

The operation returns the following:

{ "_id" : 1, "description" : "Single LINE description.", "result" : false }
{ "_id" : 2, "description" : "First lines\nsecond line", "result" : true }
{ "_id" : 3, "description" : "Many spaces before     line", "result" : true }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "result" : true }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "result" : false }
{ "_id" : 6, "description" : "métier work vocation", "result" : false }

The following regex pattern /lin(e|k)/ specifies a grouping (e|k) in the pattern:

db.products.aggregate([
   { $addFields: { result: { $regexMatch: { input: "$description", regex: /lin(e|k)/ } } } }
])

The operation returns the following:

{ "_id" : 1, "description" : "Single LINE description.", "result" : false }
{ "_id" : 2, "description" : "First lines\nsecond line", "result" : true }
{ "_id" : 3, "description" : "Many spaces before     line", "result" : true }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "result" : true }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "result" : true }
{ "_id" : 6, "description" : "métier work vocation", "result" : false }

i Option

Note

You cannot specify options in both the regex and the options field.

To perform case-insensitive pattern matching, include the i option as part of the regex field or in the options field:

// Specify i as part of the regex field
{ $regexMatch: { input: "$description", regex: /line/i } }

// Specify i in the options field
{ $regexMatch: { input: "$description", regex: /line/, options: "i" } }
{ $regexMatch: { input: "$description", regex: "line", options: "i" } }

For example, the following aggregation performs a case-insensitive $regexMatch on the description field. The regex pattern /line/ does not specify any grouping:

db.products.aggregate([
   { $addFields: { result: { $regexMatch: { input: "$description", regex: /line/i } } } }
])

The operation returns the following documents:

{ "_id" : 1, "description" : "Single LINE description.", "result" : true }
{ "_id" : 2, "description" : "First lines\nsecond line", "result" : true }
{ "_id" : 3, "description" : "Many spaces before     line", "result" : true }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "result" : true }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "result" : false }
{ "_id" : 6, "description" : "métier work vocation", "result" : false }

m Option

Note

You cannot specify options in both the regex and the options field.

To match the specified anchors (e.g. ^, $) for each line of a multiline string, include the m option as part of the regex field or in the options field:

// Specify m as part of the regex field
{ $regexMatch: { input: "$description", regex: /line/m } }

// Specify m in the options field
{ $regexMatch: { input: "$description", regex: /line/, options: "m" } }
{ $regexMatch: { input: "$description", regex: "line", options: "m" } }

The following example includes both the i and the m options to match lines starting with either the letter s or S for multiline strings:

db.products.aggregate([
   { $addFields: { result: { $regexMatch: { input: "$description", regex: /^s/im } } } }
])

The operation returns the following:

{ "_id" : 1, "description" : "Single LINE description.", "result" : true }
{ "_id" : 2, "description" : "First lines\nsecond line", "result" : true }
{ "_id" : 3, "description" : "Many spaces before     line", "result" : false }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "result" : false }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "result" : false }
{ "_id" : 6, "description" : "métier work vocation", "result" : false }

x Option

Note

You cannot specify options in both the regex and the options field.

To ignore all unescaped white space characters and comments (denoted by the un-escaped hash # character and the next new-line character) in the pattern, include the s option in the options field:

// Specify x in the options field
{ $regexMatch: { input: "$description", regex: /line/, options: "x" } }
{ $regexMatch: { input: "$description", regex: "line", options: "x" } }

The following example includes the x option to skip unescaped white spaces and comments:

db.products.aggregate([
   { $addFields: { returns: { $regexMatch: { input: "$description", regex: /lin(e|k) # matches line or link/, options:"x" } } } }
])

The operation returns the following:

{ "_id" : 1, "description" : "Single LINE description.", "returns" : false }
{ "_id" : 2, "description" : "First lines\nsecond line", "returns" : true }
{ "_id" : 3, "description" : "Many spaces before     line", "returns" : true }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "returns" : true }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "returns" : true }
{ "_id" : 6, "description" : "métier work vocation", "returns" : false }

s Option

Note

You cannot specify options in both the regex and the options field.

To allow the dot character (i.e. .) in the pattern to match all characters including the new line character, include the s option in the options field:

// Specify s in the options field
{ $regexMatch: { input: "$description", regex: /m.*line/, options: "s" } }
{ $regexMatch: { input: "$description", regex: "m.*line", options: "s" } }

The following example includes the s option to allow the dot character (i.e. .) to match all characters including new line as well as the i option to perform a case-insensitive match:

db.products.aggregate([
   { $addFields: { returns: { $regexMatch: { input: "$description", regex:/m.*line/, options: "si"  } } } }
])

The operation returns the following:

{ "_id" : 1, "description" : "Single LINE description.", "returns" : false }
{ "_id" : 2, "description" : "First lines\nsecond line", "returns" : false }
{ "_id" : 3, "description" : "Many spaces before     line", "returns" : true }
{ "_id" : 4, "description" : "Multiple\nline descriptions", "returns" : true }
{ "_id" : 5, "description" : "anchors, links and hyperlinks", "returns" : false }
{ "_id" : 6, "description" : "métier work vocation", "returns" : false }

Use $regexMatch to Check Email Address

Create a sample collection feedback with the following documents:

db.feedback.insertMany([
   { "_id" : 1, comment: "Hi, I'm just reading about MongoDB -- aunt.arc.tica@example.com"  },
   { "_id" : 2, comment: "I wanted to concatenate a string" },
   { "_id" : 3, comment: "How do I convert a date to string? Contact me at either cam@mongodb.com or c.dia@mongodb.com" },
   { "_id" : 4, comment: "It's just me. I'm testing.  fred@MongoDB.com" }
])

The following aggregation uses the $regexMatch to check if the comment field contains an email address with @mongodb.com and categorize the feedback as Employee or External.

db.feedback.aggregate( [
    { $addFields: {
       "category": { $cond: { if:  { $regexMatch: { input: "$comment", regex: /[a-z0-9_.+-]+@mongodb.com/i } },
                              then: "Employee",
                              else: "External" } }
    } },

The operation returns the following documents:

{ "_id" : 1, "comment" : "Hi, I'm just reading about MongoDB -- aunt.arc.tica@example.com", "category" : "External" }
{ "_id" : 2, "comment" : "I wanted to concatenate a string", "category" : "External" }
{ "_id" : 3, "comment" : "How do I convert a date to string? Contact me at either cam@mongodb.com or c.dia@mongodb.com", "category" : "Employee" }
{ "_id" : 4, "comment" : "It's just me. I'm testing.  fred@MongoDB.com", "category" : "Employee" }