Group Data with the Bucket Pattern使用桶模式对数据进行分组

Query for Data with the Bucket Pattern使用桶模式查询数据

In the updated schema, each document contains data for a single page in the application. You can use the _id and count field to determine how to return and update data.在更新的模式中，每个文档都包含应用程序中单个页面的数据。您可以使用_id和count字段来确定如何返回和更新数据。

To query for data on the appropriate page, use a regex query to return data for a specified customerId, and use skip to return to the data for the correct page. 要查询相应页面上的数据，请使用正则表达式查询返回指定customerId的数据，并使用skip返回正确页面的数据。The regex query on _id uses the default _id index, which results in performant queries without the need for an additional index.对_id的正则表达式查询使用默认的_id索引，这会导致高性能的查询，而不需要额外的索引。

The following query returns data for the first page of trades for customer 123:以下查询返回客户123的第一页事务数据：

db.trades.find( { "_id": /^123_/ } ).sort( { _id: 1 } ).limit(1)

To return data for later pages, specify a skip value of one less than the page you want to show data for. For example, to show data for page 10, run the following query:若要返回后续页面的数据，请指定一个比要显示数据的页面小一个的skip值。例如，要显示第10页的数据，请运行以下查询：

db.trades.find( { "_id": /^123_/ } ).sort( { _id: 1 } ).skip(9).limit(1)

Insert Data with the Bucket Pattern使用桶模式插入数据

Now that the schema uses the bucket pattern, update your application logic to insert new trades into the correct bucket. Use an update command to insert the trade into the bucket with the appropriate customerId and bucket.既然模式使用了桶模式，那么更新应用程序逻辑，将新事务插入到正确的桶中。使用update命令将事务插入到带有相应customerId和桶的桶中。

The following command inserts a new trade for customerId: 123:以下命令为customerId:123插入新事务：

db.trades.updateOne( { "_id": /^123_/, "count": { $lt: 10 } },
   {
      "$push": {
         "history": {
         "type": "buy",
         "ticker": "MSFT",
         "qty": 42,
         "date": ISODate("2023-11-02T11:43:10")
       }
    },
    "$inc": { "count": 1 },
    "$setOnInsert": { "_id": "123_1698939791", "customerId": 123 }
   },
   { upsert: true }
)

The application displays 10 trades per page. The update filter searches for a document for customerId: 123 where the count is less than 10, meaning that bucket does not contain a full page of data应用程序每页显示10笔事务。更新筛选器搜索count小于10的customerId:123文档，这意味着桶不包含整页数据.

• If there is a document that matches "_id": /^123_/ and its count is less than 10, the update command pushes the new trade into the matched document's history array.
• If there is not a matching document, the update command inserts a new document with the new trade (because upsert is true). 如果没有匹配的文档，update命令会插入一个包含新事务的新文档（因为upsert为true）。The _id field of the new document is a concatenation of the customerId and the time in seconds since the unix epoch of the trade.新文档的_id字段是customerId和自事务的unix纪元以来的时间（秒）的连接。

The logic for update commands avoids unbounded arrays by ensuring that no history array contains more than 10 documents.更新命令的逻辑通过确保没有历史数组包含超过10个文档来避免无界数组。

After you run the update operation, the trades collection has the following documents:运行更新操作后，trades集合包含以下文档：

[
  {
    _id: '123_1698349623',
    customerId: 123,
    count: 3,
    history: [
      {
        type: 'buy',
        ticker: 'MDB',
        qty: 419,
        date: ISODate("2023-10-26T15:47:03.434Z")
      },
      {
        type: 'sell',
        ticker: 'MDB',
        qty: 29,
        date: ISODate("2023-10-30T09:32:57.765Z")
      },
      {
        type: 'buy',
        ticker: 'MSFT',
        qty: 42,
        date: ISODate("2023-11-02T11:43:10.000Z")
      }
    ]
  },
  {
    _id: '456_1698765362',
    customerId: 456,
    count: 1,
    history: [
      {
        type: 'buy',
        ticker: 'GOOG',
        quantity: 50,
        date: ISODate("2023-10-31T11:16:02.120Z")
      }
    ]
  }
]