Expire Data from Collections by Setting TTL通过设置TTL使集合中的数据过期

Expire Documents in the MongoDB Atlas UIMongoDB Atlas UI中的过期文档

To expire data in the Atlas UI, follow these steps:要使Atlas UI中的数据过期，请执行以下步骤：

Expire Documents after a Specified Number of Seconds在指定秒数后过期文档

You can expire documents after a specified number of seconds through collection creation options or a TTL index.您可以通过集合创建选项或TTL索引在指定秒数后使文档过期。

db.log_events.createIndex( { "createdAt": 1 }, { expireAfterSeconds: 10 } )

db.log_events.insertOne( {
   "createdAt": new Date(),
   "logEvent": 2,
   "logMessage": "Success!"
} )

Expire Documents with Filter Conditions使用筛选条件过期文档

To expire documents with specific filter expressions, you can create an index that is both a partial and a TTL index.要使用特定的筛选表达式使文档过期，您可以创建一个既是部分索引又是TTL索引的索引。

Create a partial TTL index:创建部分TTL索引：

db.foo.createIndex(
   { F: 1 },
   {
      name: "Partial-TTL-Index",
      partialFilterExpression: { D : 1 },
      expireAfterSeconds: 10
   }
)

Insert two documents, one of which matches the filter expression { D : 1 } of the partialFilterExpression:插入两个文档，其中一个与partialFilterExpression的筛选表达式{ D : 1 }匹配：

db.foo.insertMany( [
   { "F" : ISODate("2019-03-07T20:59:18.428Z"), "D" : 3},
   { "F" : ISODate("2019-03-07T20:59:18.428Z"), "D" : 1}
] )

Wait for ten seconds then query the foo collection:等待10秒，然后查询foo集合：

db.foo.find({}, {_id: 0, F: 1, D: 1})

The document that matches the partialFilterExpression of { D : 1 } is deleted (expired). As a result, only one document remains in the foo collection:与{ D : 1 }的partialFilterExpression匹配的文档已被删除（过期）。因此，foo集合中只剩下一个文档：

{ "F" : ISODate("2019-03-07T20:59:18.428Z"), "D" : 3}

Expire Documents at a Specific Clock Time在特定时钟时间过期文档

You can expire data at a specified clock time in the terminal. To expire documents at a specific clock time, begin by creating a TTL index on a field that holds values of BSON date type or an array of BSON date-typed objects and specify an expireAfterSeconds value of 0. 您可以在终端中的指定时钟时间过期数据。要在特定时钟时间过期文档，请首先在包含BSON日期类型值或BSON日期型对象数组的字段上创建TTL索引，并指定expireAfterSeconds值为0。For each document in the collection, set the indexed date field to a value corresponding to the time the document should expire. If the indexed date field contains a date in the past, MongoDB considers the document expired.对于集合中的每个文档，将索引日期字段设置为与文档到期时间对应的值。如果索引日期字段包含过去的日期，MongoDB将认为文档已过期。

For example, the following operation creates an index on the log_events collection's expireAt field and specifies the expireAfterSeconds value of 0:例如，以下操作在log_events集合的expireAt字段上创建索引，并指定expireAfterSeconds值为0：

db.log_events.createIndex( { "expireAt": 1 }, { expireAfterSeconds: 0 } )

For each document, set the value of expireAt to correspond to the time the document should expire. For example, the following insertOne() operation adds a document that expires at July 22, 2013 14:00:00.对于每个文档，将expireAt的值设置为与文档应过期的时间相对应。例如，以下insertOne()操作添加了一个在July 22, 2013 14:00:00到期的文档。

db.log_events.insertOne( {
   "expireAt": new Date('July 22, 2013 14:00:00'),
   "logEvent": 2,
   "logMessage": "Success!"
} )

MongoDB will automatically delete documents from the log_events collection when the documents' expireAt value is older than the number of seconds specified in expireAfterSeconds, i.e. 0 seconds older in this case. 当文档的expireAt值早于expireAfterSeconds中指定的秒数时，MongoDB将自动从log_events集合中删除文档，即在这种情况下早0秒。As such, the data expires at the specified expireAt value.因此，数据在指定的expireAt值处过期。

Indexes Configured Using NaN使用NaN配置的索引

Do not set expireAfterSeconds to NaN in your TTL index configuration.请勿在TTL索引配置中将expireAfterSeconds设置为NaN。

Prior to MongoDB 5.0, when a TTL index has expireAfterSeconds set to NaN, MongoDB logs an error and does not remove any records.在MongoDB 5.0之前，当TTL索引的expireAfterSeconds设置为NaN时，MongoDB会记录错误，并且不会删除任何记录。

From MongoDB 5.0.0 - 5.0.13 (and 6.0.0 - 6.0.1), NaN is treated as 0. If a TTL index is configured with expireAfterSeconds set to NaN, all TTL-indexed documents expire immediately.从MongoDB 5.0.0到5.0.13（和6.0.0到6.0.1），NaN被视为0。如果TTL索引配置为expireAfterSeconds设置为NaN，则所有TTL索引文档都会立即过期。

Starting in MongoDB 5.0.14 (and 6.0.2), the server will not use TTL indexes that have expireAfterSeconds set to NaN.从MongoDB 5.0.14（和6.0.2）开始，服务器将不使用expireAfterSeconds设置为NaN的TTL索引。

However, there are still some situations which may result in unexpected behavior. Documents may expire:然而，仍有一些情况可能会导致意外行为。文件可能会过期：

• During an initial sync to an earlier version from MongoDB 5.0.0 - 5.0.13 (or 6.0.0 - 6.0.1).在从MongoDB 5.0.0到5.0.13（或6.0.0到6.0.1）的早期版本的初始同步期间。

• When upgrading from an earlier version to MongoDB 5.0.0 - 5.0.13.从早期版本升级到MongoDB 5.0.0-5.0.13时。
• When restoring a collection from a pre-5.0 mongodump into a MongoDB 5.0.0 - 5.0.13 (or 6.0.0 - 6.0.1) instance.将集合从5.0之前的mongodump还原到MongoDB 5.0.0-5.0.13（或6.0.0-6.0.1）实例时。

To avoid problems, either drop or correct any misconfigured TTL indexes.为避免出现问题，请删除或更正任何配置错误的TTL索引。

function getNaNIndexes() {
   const nan_index = [];

   const dbs = db.adminCommand({ listDatabases: 1 }).databases;

   dbs.forEach((d) => {
      if (d.name != 'local') {
         const listCollCursor = db
            .getSiblingDB(d.name)
            .runCommand({ listCollections: 1 }).cursor;

         const collDetails = {
            db: listCollCursor.ns.split(".$cmd")[0],
            colls: listCollCursor.firstBatch.map((c) => c.name),
         };

         collDetails.colls.forEach((c) =>
            db
               .getSiblingDB(collDetails.db)
               .getCollection(c)
               .getIndexes()
               .forEach((entry) => {
                  if (Object.is(entry.expireAfterSeconds, NaN)) {
                     nan_index.push({ ns: `${collDetails.db}.${c}`, index: entry });
                  }
               })
         );
      }
   });

   return nan_index;
};

getNaNIndexes();