$text (Self-Managed Deployments)（自我管理部署）

Exact Strings精确字符串

To match on an exact multi-word string, as opposed to individual terms, enclose the string in escaped double quotes (\"), as in:要匹配精确的多单词字符串，而不是单个术语，请将字符串括在转义双引号（\"）中，如：

"\"ssl certificate\""

If the $search string of a $text operation includes a multi-word string and individual terms, $text only matches the documents that include the multi-word string.如果$text操作的$search字符串包括多单词字符串和单个术语，则$text仅匹配包含多单词字符串的文档。

For example, the following $search string returns documents that include the exact string "ssl certificate":例如，以下$search字符串返回包含确切字符串"ssl certificate"的文档：

"\"ssl certificate\" authority key"

Negations否定

Prefixing a word with a hyphen-minus (-) negates a word:在单词前加连字符减（-）可以否定单词：

• The negated word excludes documents that contain the negated word from the result set.否定词将包含否定词的文档从结果集中排除。
• When passed a string that only contains negated words, $text does not match any documents.当传递一个只包含否定词的字符串时，$text与任何文档都不匹配。
• A hyphenated word, such as pre-market, is not a negation. If used in a hyphenated word, the $text operator treats the hyphen-minus (-) as a delimiter. 连字符的单词，如pre-market，不是否定。如果在连字符单词中使用，$text运算符会将连字符减（-）视为分隔符。To negate the word market in this instance, include a space between pre and -market, i.e., pre -market.在这种情况下，为了否定market一词，在pre和-market之间加一个空格，即pre -market。

The $text operator adds all negations to the operation with the logical AND operator.$text运算符使用逻辑AND运算符将所有否定添加到操作中。

Stop Words停用词

The $text operator ignores language-specific stop words, such as the and and in English.$text运算符忽略特定语言的停用词，如英语中的the和and。

Stemmed Words词干词

When you use case insensitivity and diacritic insensitivity, the $text operator matches on the complete stemmed word. 当您使用不区分大小写和不区分变音符号时，$text运算符会匹配完整的词干单词。If a document field contains the word blueberry, a $text operation with a $search term of blue does not match. 如果文档字段包含单词blueberry（蓝莓），则具有blue的$search术语的$text操作不匹配。However, blueberry or blueberries match.然而，blueberry或blueberries匹配。

$caseSensitive Option选项

To support case sensitivity where the text index is case insensitive, specify $caseSensitive: true.要在text索引不区分大小写的情况下支持区分大小写，请指定$caseSensitive:true。

Case Sensitivity Process大小写敏感性过程

If $caseSensitive: true and the text index is case insensitive, the $text operator:如果$caseSensitive: true且文本索引不区分大小写，则$text运算符：

• First queries the text index for case insensitive and diacritic matches.首先查询text索引以查找不区分大小写和变音符号的匹配项。
• Then, to return just the documents that match the case of the specified terms, the $text operation includes an additional stage to filter out the documents that do not match the specified case.然后，为了只返回与指定术语大小写匹配的文档，$text操作包括一个额外的阶段，用于筛选出与指定大小写不匹配的文档。

If $caseSensitive: true and if the suffix stem contains uppercase letters, the $text operator matches on the exact word.如果$caseSensitive: true，并且后缀词干包含大写字母，则$text运算符与确切的单词匹配。

Specifying $caseSensitive: true may impact performance.指定$caseSensitive: true可能会影响性能。

$diacriticSensitive Option选项

To support diacritic sensitivity with the text index, specify $diacriticSensitive: true.要使用text索引支持变音符号敏感性，请指定$diacriticSensitive: true。

Text queries against earlier versions of the text index are inherently diacritic sensitive and cannot be diacritic insensitive. As such, the $diacriticSensitive option for the $text operator has no effect with earlier versions of the text index.针对早期版本的文本索引的文本查询本质上对变音符号敏感，不能对变音字符不敏感。因此，$text运算符的$diacriticSensitive选项对早期版本的文本索引无效。

Diacritic Sensitivity ProcessDiacritic敏感性过程

To use diacritic sensitivity ($diacriticSensitive: true) with a version 3 text index, the $text operator:要将变音符号敏感性（$diacriticSensitive: true）与版本3文本索引一起使用，$text运算符：

• First queries the text index, which is diacritic insensitive.首先查询text索引，该索引对变音符号不敏感。
• Then, to return just the documents that match the diacritic marked characters of the specified terms, the $text operation includes an additional stage to filter out the documents that do not match.然后，为了只返回与指定术语的变音符号标记字符匹配的文档，$text操作包括一个额外的阶段来筛选不匹配的文档。

Specifying $diacriticSensitive: true may impact performance.指定$diacriticSensitive: true可能会影响性能。

If you use $diacriticSensitive: true with an earlier version of the text index, the $text operator queries the text index, which is diacritic sensitive.如果将$diacriticSensitive: true与早期版本的text索引一起使用，则$text运算符会查询文本索引，该索引对变音符号敏感。

If $diacriticSensitive: true and if the suffix stem contains the diacritic mark or marks, the $text operator matches on the exact word.如果$diacriticSensitive: true，并且后缀词干包含一个或多个变音符号，则$text运算符将与确切的单词匹配。

Case Sensitivity with a Term带有术语的案例敏感性

The following example performs a case sensitive query for the term Coffee:以下示例对术语Coffee执行区分大小写的查询：

db.articles.find( { $text: { $search: "Coffee", $caseSensitive: true } } )

The operation matches just the following document:该操作仅匹配以下文档：

{ "_id" : 2, "subject" : "Coffee Shopping", "author" : "efg", "views" : 5 }

Case Sensitivity with an Exact String使用精确字符串区分大小写

The following example performs a case sensitive query for the exact multi-word string Café Con Leche:以下示例对确切的多单词字符串Café Con Leche执行区分大小写的查询：

db.articles.find( {
   $text: { $search: "\"Café Con Leche\"", $caseSensitive: true }
} )

The operation matches just the following document:该操作仅匹配以下文档：

{ "_id" : 5, "subject" : "Café Con Leche", "author" : "abc", "views" : 200 }

Case Sensitivity with Negated Term带否定项的案例敏感性

A negated term is a term that is prefixed by a minus sign -. If you negate a term, the $text operator will exclude the documents that contain those terms from the results. You can also specify case sensitivity for negated terms.否定项是以减号-为前缀的项。如果否定一个术语，$text运算符将从结果中排除包含这些术语的文档。您还可以为否定项指定区分大小写。

The following example performs a case sensitive query for documents that contain the word Coffee but do not contain the lower-case term shop, or more precisely the stemmed version of the words:以下示例对包含单词Coffee但不包含小写单词shop的文档执行区分大小写的查询，或者更确切地说，不包含单词的词干版本：

db.articles.find( { $text: { $search: "Coffee -shop", $caseSensitive: true } } )

The operation matches the following document:该操作与以下文档匹配：

{ "_id" : 2, "subject" : "Coffee Shopping", "author" : "efg" }

Diacritic Sensitivity with a Term带有术语的变音符号敏感性

The following example performs a diacritic sensitive text query on the term CAFÉ, or more precisely the stemmed version of the word:以下示例对CAFÉ一词，或者更确切地说是该词的词干版本，执行对变音符号敏感的文本查询：

db.articles.find( { $text: { $search: "CAFÉ", $diacriticSensitive: true } } )

The operation only matches the following document:该操作仅匹配以下文档：

{ "_id" : 5, "subject" : "Café Con Leche", "author" : "abc" }

Diacritic Sensitivity with Negated Term否定条件下的辩证敏感性

The $diacriticSensitive option applies also to negated terms. A negated term is a term that is prefixed by a minus sign -. If you negate a term, the $text operator will exclude the documents that contain those terms from the results.$diacriticSensitive选项也适用于被否定的条款。否定项是以减号-为前缀的项。如果否定一个术语，$text运算符将从结果中排除包含这些术语的文档。

The following example performs a diacritic sensitive text query for documents that contain the term leches but not the term cafés, or more precisely the stemmed version of the words:以下示例对包含术语leches但不包含术语cafés的文档执行对变音符号敏感的文本查询，或者更确切地说，是单词的词干版本：

db.articles.find(
  { $text: { $search: "leches -cafés", $diacriticSensitive: true } }
)

The operation matches the following document:该操作与以下文档匹配：

{ "_id" : 8, "subject" : "Cafe con Leche", "author" : "xyz" }

Return the Relevance Score返回相关性得分

The following example performs a text query for the term cake and uses the $meta operator in the projection document to append the relevance score to each matching document:以下示例对术语cake执行文本查询，并在投影文档中使用$meta运算符将相关性得分附加到每个匹配的文档中：

db.articles.find(
   { $text: { $search: "cake" } },
   { score: { $meta: "textScore" } }
)

The returned document includes an additional field score that contains the document's relevance score:返回的文档包括一个额外的字段score，其中包含文档的相关性分数：

{ "_id" : 3, "subject" : "Baking a cake", "author" : "abc", "views" : 90, "score" : 0.75 }

Sort by Relevance Score按相关性得分排序

• You can specify the { $meta: "textScore" } expression in the sort() without also specifying the expression in the projection. For example:您可以在sort()中指定{ $meta: "textScore" }表达式，而无需在投影中指定表达式。例如：

  db.articles.find(
     { $text: { $search: "cake" } }
  ).sort( { score: { $meta: "textScore" } } )

  As a result, you can sort the resulting documents by their relevance without projecting the textScore.因此，您可以按相关性对生成的文档进行排序，而无需投影textScore。

• If you include the { $meta: "textScore" } expression in both the projection and sort(), the projection and sort documents can have different field names for the expression.如果在投影和sort()中都包含{ $meta: "textScore" }表达式，则投影和排序文档可以为表达式使用不同的字段名。

  For example, in the following operation, the projection uses a field named score for the expression and the sort() uses the field named ignoredName.例如，在以下操作中，投影使用名为score的字段作为表达式，sort()使用名为ignoredName的字段。

  db.articles.find(
     { $text: { $search: "cake" } } ,
     { score: { $meta: "textScore" } }
  ).sort( { ignoredName: { $meta: "textScore" } } )

Return Top 2 Matching Documents返回前2个匹配文档

Use the limit() method in conjunction with a sort() to return the top n matching documents.将limit()方法与sort()结合使用，返回前n个匹配的文档。

The following example queries for the term coffee and sorts the results by the descending score, limiting the results to the top two matching documents:以下示例查询术语coffee，并按降序对结果进行排序，将结果限制在前两个匹配的文档中：

db.articles.find(
   { $text: { $search: "coffee" } },
   { score: { $meta: "textScore" } }
).sort( { score: { $meta: "textScore" } } ).limit(2)

$text with Additional Query and Sort Expressions带有附加查询和排序表达式的$text

The following example matches documents where the author equals "xyz" and the indexed field subject contains the terms coffee or bake. The operation also specifies a sort order of ascending date, then descending relevance score:以下示例匹配author等于"xyz"且索引字段subject题包含术语coffee或bake的文档。该操作还指定了date升序、相关性得分降序的排序顺序：

db.articles.find(
   { author: "xyz", $text: { $search: "coffee bake" } },
   { score: { $meta: "textScore" } }
).sort( { date: 1, score: { $meta: "textScore" } } )