Collations排序规则¶

find() and sort() Examplefind()和sort()示例¶

The following example calls both find() and sort() on a collection that uses the default binary collation. 下面的示例对使用默认二进制排序规则的集合同时调用find()和sort()。We use the German collation by setting the value of the locale parameter to de.我们通过将locale参数的值设置为de来使用德语排序规则。

collection.find({ city: "New York" }, { collation: { locale: "de" } })
  .sort({ name: 1 });

findOneAndUpdate() ExamplefindOneAndUpdate()示例¶

The following example calls the findOneAndUpdate() operation on a collection that uses the default binary collation. 以下示例对使用默认二进制排序规则的集合调用findOneAndUpdate()操作。The collection contains the following documents:该集合包含以下文档：

{ "_id" : 1, "first_name" : "Hans" }
{ "_id" : 2, "first_name" : "Gunter" }
{ "_id" : 3, "first_name" : "Günter" }
{ "_id" : 4, "first_name" : "Jürgen" }

Consider the following findOneAndUpdate() operation on this collection which does not specify a collation:考虑此集合上的不指定排序规则的以下FordOnUpDebug()操作：

collection.findOneAndUpdate(
  { first_name : { $lt: "Gunter" } },
  { $set: { verified: true } }
);

Since "Gunter" is the first sorted result when using a binary collation, none of the documents come lexically before and match the $lt comparison operator in the query document. 由于“Gunter”是使用二进制排序规则时的第一个排序结果，因此没有一个文档在词汇上位于查询文档中的$lt比较运算符之前。As a result, the operation does not update any documents.因此，该操作不会更新任何文档。

Consider the same operation with a collation specified with the locale set to de@collation=phonebook. 考虑与设置区域设置指定的排序规则相同的操作de@collation=phonebook。This locale specifies the collation=phonebook option which contains rules for prioritizing proper nouns, identified by capitalization of the first letter. 此区域设置指定collation=phonebook选项，该选项包含对专有名词进行优先级排序的规则，由第一个字母的大写字母标识。The de@collation=phonebook locale and option sorts characters with umlauts before the same characters without umlauts.这个de@collation=phonebook区域设置和选项将使用umlauts的字符排序在不使用umlauts的相同字符之前。

collection.findOneAndUpdate(
  { first_name: { $lt: "Gunter" } },
  { $set: { verified: true } },
  { collation: { locale: "de@collation=phonebook" } },
);

Since "Günter" lexically comes before "Gunter" using the de@collation=phonebook collation specified in findOneAndUpdate(), the operation returns the following updated document:因为使用findOneAndUpdate()中指定的de@collation=phonebook排序规则，词法上"Günter"出现在"Gunter"前面，该操作返回以下更新的文档：

{ lastErrorObject: { updatedExisting: true, n: 1 },
  value: { _id: 3, first_name: 'Günter' },
  ok: 1 }

findOneAndDelete() ExamplefindOneAndDelete()示例¶

The following example calls the findOneAndDelete() operation on a collection that uses the default binary collation and contains the following documents:以下示例对使用默认二进制排序规则并包含以下文档的集合调用findOneAndDelete()操作：

{ "_id" : 1, "a" : "16" }
{ "_id" : 2, "a" : "84" }
{ "_id" : 3, "a" : "179" }

In this example, we set the numericOrdering collation parameter to true to sort numeric strings based on their numerical order instead of their lexical order.在本例中，我们将numericOrdering排序规则参数设置为true，以根据数字顺序而不是词汇顺序对数字字符串进行排序。

collection.findOneAndDelete(
  { a: { $gt: "100" } },
  { collation: { locale: "en", numericOrdering: true } },
);

After you run the operation above, the collection contains the following documents:运行上述操作后，集合包含以下文档：

{ "_id" : 1, "a" : "16" }
{ "_id" : 2, "a" : "84" }

If you perform the same operation without collation on the original collection of three documents, it matches documents based on the lexical value of the strings ("16", "84", and "179"), and deletes the first document it finds that matches the query criteria.如果在没有对三个文档的原始集合进行排序的情况下执行相同的操作，它将根据字符串的词法值（“16”、“84”和“179”）匹配文档，并删除它找到的与查询条件匹配的第一个文档。

await collection.findOneAndDelete({ a: { $gt: "100" } });

Since all the documents contain lexical values in the a field that match the criteria (greater than the lexical value of "100"), the operation removes the first result. 由于所有文档的a字段中都包含符合条件的词法值（大于词法值“100”），因此该操作将删除第一个结果。After you run the operation above, the collection contains the following documents:运行上述操作后，集合包含以下文档：

{ "_id" : 2, "a" : "84" }
{ "_id" : 3, "a" : "179" }

Aggregation Example聚合示例¶

To use collation with the aggregate operation, pass the collation document in the options field, after the array of pipeline stages.要在聚合操作中使用排序规则，请在管道阶段数组之后，在选项字段中传递排序规则文档。

The following example shows an aggregation pipeline on a collection that uses the default binary collation. 以下示例显示使用默认二进制排序规则的集合上的聚合管道。The aggregation groups the first_name field, counts the total number of results in each group, and sorts the results by the German phonebook (de@collation=phonebook locale) order.聚合对first_name字段进行分组，统计每个组中的结果总数，并按德语电话簿对结果进行排序（de@collation=phonebook区域设置）顺序。

collection.aggregate(
  [
    { $group: { "_id": "$first_name", "nameCount": { "$sum": 1 } } },
    { $sort: { "_id": 1 } },
  ],
  { collation: { locale: "de@collation=phonebook" } },
);