$tsSecond (aggregation)

Obtain the Number of Seconds from a Timestamp Field从时间戳字段中获取秒数

Create a stockSales collection that contains company stock financial market sales:创建一个包含公司股票金融市场销售的stockSales集合：

db.stockSales.insertMany( [
   { _id: 0, symbol: "MDB", saleTimestamp: Timestamp(1622731060, 1) },
   { _id: 1, symbol: "MDB", saleTimestamp: Timestamp(1622731060, 2) },
   { _id: 2, symbol: "MSFT", saleTimestamp: Timestamp(1714124193, 1) },
   { _id: 3, symbol: "MSFT", saleTimestamp: Timestamp(1714124193, 2) },
   { _id: 4, symbol: "MSFT", saleTimestamp: Timestamp(1714124193, 3) }
] )

In the timestamp constructor, the:在timestamp构造函数中

• First value is the number of seconds after the Unix epoch.第一个值是Unix epoch之后的秒数。
• Second value is the incrementing ordinal. 第二个值是递增序数。When multiple events happen within the same second, the incrementing ordinal uniquely identifies each event.当同一秒内发生多个事件时，递增的序数唯一地标识每个事件。

The following example uses $tsSecond in a $project pipeline stage to return the seconds from the stock sales saleTimestamp field:以下示例在$project管道阶段中使用$tsSecond来返回股票销售saleTimestamp字段中的秒数：

db.stockSales.aggregate( [
   {
      $project:
      {
         _id: 0, saleTimestamp: 1, saleSeconds: { $tsSecond: "$saleTimestamp" }
      }
   }
] )

Example output:示例输出：

{
  saleTimestamp: Timestamp({ t: 1622731060, i: 1 }),
  saleSeconds: Long("1622731060")
},
{
  saleTimestamp: Timestamp({ t: 1622731060, i: 2 }),
  saleSeconds: Long("1622731060")
},
{
  saleTimestamp: Timestamp({ t: 1714124193, i: 1 }),
  saleSeconds: Long("1714124193")
},
{
  saleTimestamp: Timestamp({ t: 1714124193, i: 2 }),
  saleSeconds: Long("1714124193")
},
{
  saleTimestamp: Timestamp({ t: 1714124193, i: 3 }),
  saleSeconds: Long("1714124193")
}

Use $tsSecond in a Change Stream Cursor to Monitor Collection Changes在更改流游标中使用$tsSecond监视集合更改

The example in this section uses $tsSecond in a change stream cursor to monitor changes to a collection.本节中的示例在更改流游标中使用$tsSecond来监视对集合的更改。

Create a change stream cursor on a collection named cakeSales that you will see later in this section:在名为cakeSales的集合上创建一个变更流游标，您将在本节稍后看到：

cakeSalesCursor = db.cakeSales.watch( [
   {
      $addFields: {
         clusterTimeSeconds: { $tsSecond: "$clusterTime" }
      }
   }
] )

In the example, the:在该示例中

• db.collection.watch() method creates a change stream cursor for the cakeSales collection and stores the cursor in cakeSalesCursor.方法为cakeSaless集合创建一个变更流游标，并将该游标存储在cakeSalesCursor中。
• $addFields stage adds a field named clusterTimeSeconds to cakeSalesCursor.$addFields阶段将一个名为clusterTimeSeconds的字段添加到cakeSalesCursor中。
  • $clusterTime is the timestamp from the oplog entry for the cakeSales collection change. $clusterTime是cakeSales集合更改的oplog条目中的时间戳。See Command Response.
  • $tsSecond returns the seconds from $clusterTime, which is stored in clusterTimeSeconds.

Create a cakeSales collection that contains cake sales in the states of California (CA) and Washington (WA):

db.cakeSales.insertMany( [
   { _id: 0, type: "chocolate", orderDate: new Date("2020-05-18T14:10:30Z"),
     state: "CA", price: 13, quantity: 120 },
   { _id: 1, type: "chocolate", orderDate: new Date("2021-03-20T11:30:05Z"),
     state: "WA", price: 14, quantity: 140 },
   { _id: 2, type: "vanilla", orderDate: new Date("2021-01-11T06:31:15Z"),
     state: "CA", price: 12, quantity: 145 },
   { _id: 3, type: "vanilla", orderDate: new Date("2020-02-08T13:13:23Z"),
     state: "WA", price: 13, quantity: 104 },
   { _id: 4, type: "strawberry", orderDate: new Date("2019-05-18T16:09:01Z"),
     state: "CA", price: 41, quantity: 162 },
   { _id: 5, type: "strawberry", orderDate: new Date("2019-01-08T06:12:03Z"),
     state: "WA", price: 43, quantity: 134 }
] )

To monitor the cakeSales collection changes, use cakeSalesCursor. 要监视cakeSales集合的更改，请使用cakeSalesCursor。For example, to obtain the next document from cakeSalesCursor, use the next() method:例如，要从cakeSalesCursor获取下一个文档，请使用next()方法：

cakeSalesCursor.next()

The following example output shows the insert details for the first document added to the cakeSales collection. The clusterTimeSeconds field contains the seconds from the clusterTime field.以下示例输出显示了添加到cakeSales集合的第一个文档的插入详细信息。clusterTimeSeconds字段包含clusterTime字段中的秒数。

_id: {
  _data: '82613A4A51000000032B022C0100296E5A100495189B4131584C56AC8BA9D540799F23461E5F696400290004'
},
operationType: 'insert',
clusterTime: Timestamp({ t: 1631210065, i: 3 }),
fullDocument: {
  _id: 0,
  type: 'chocolate',
  orderDate: ISODate("2020-05-18T14:10:30.000Z"),
  state: 'CA',
  price: 13,
  quantity: 120
},
ns: { db: 'test', coll: 'cakeSales' },
documentKey: { _id: 0 },
clusterTimeSeconds: 1631210065