使用 `$toLong` 在 MongoDB C# 查询中

huangapple
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英文:

Using `$toLong` in MongoDB C# Queries

问题

我正在努力将下面的Mongo聚合管道转换为其C＃等效项。我试图使用内置的$toLong将ISODate转换为Unix时间戳。可能有数百万个文档，因此不可行的是使用.ToList().Select(x => ConvertToTimestamp(x.date))。

假设我有以下文档：

  1. [
  2.   {
  3.     "value": 100,
  4.     "date": ISODate("2022-03-26T04:38:28.044Z")
  5.   },
  6.   {
  7.     "value": 50,
  8.     "date": ISODate("2022-03-26T04:38:28.044Z")
  9.   },
  10.   {
  11.     "value": 23,
  12.     "date": ISODate("2022-03-26T04:38:28.044Z")
  13.   },
  14.   {
  15.     "value": 199,
  16.     "date": ISODate("2022-03-26T04:38:28.044Z")
  17.   }
  18. ]

我有以下工作的聚合查询：

  1. db.collection.aggregate({
  2.   $project: {
  3.     date: {
  4.       $toLong: "$date"
  5.     },
  6.     value: 1,
  7.   }
  8. })

我得到了预期的输出：

  1. [
  2.   {
  3.     "_id": ObjectId("5a934e000102030405000000"),
  4.     "date": NumberLong(1648269508044),
  5.     "value": 100
  6.   },
  7.   {
  8.     "_id": ObjectId("5a934e000102030405000001"),
  9.     "date": NumberLong(1648269508044),
  10.     "value": 50
  11.   },
  12.   {
  13.     "_id": ObjectId("5a934e000102030405000002"),
  14.     "date": NumberLong(1648269508044),
  15.     "value": 23
  16.   },
  17.   {
  18.     "_id": ObjectId("5a934e000102030405000003"),
  19.     "date": NumberLong(1648269508044),
  20.     "value": 199
  21.   }
  22. ]

现在，问题是如何使用C＃中的流畅聚合API来执行此操作？

英文:

I'm struggling to convert the below Mongo aggregation pipeline into its C# equivalent. I am trying to convert ISODates to unix timestamps using the built in $toLong. There could be millions of documents, so doing .ToList().Select(x => ConvertToTimestamp(x.date)) is not feasible.

Say I have the following documents:

  1. [
  2.   {
  3.     "value": 100,
  4.     "date": ISODate("2022-03-26T04:38:28.044Z")
  5.   },
  6.   {
  7.     "value": 50,
  8.     "date": ISODate("2022-03-26T04:38:28.044Z")
  9.   },
  10.   {
  11.     "value": 23,
  12.     "date": ISODate("2022-03-26T04:38:28.044Z")
  13.   },
  14.   {
  15.     "value": 199,
  16.     "date": ISODate("2022-03-26T04:38:28.044Z")
  17.   }
  18. ]

I have the following aggregation query that works

  1. db.collection.aggregate({
  2.   $project: {
  3.     date: {
  4.       $toLong: "$date"
  5.     },
  6.     value: 1,
  7.   }
  8. })

And I get the expected output

  1. [
  2.   {
  3.     "_id": ObjectId("5a934e000102030405000000"),
  4.     "date": NumberLong(1648269508044),
  5.     "value": 100
  6.   },
  7.   {
  8.     "_id": ObjectId("5a934e000102030405000001"),
  9.     "date": NumberLong(1648269508044),
  10.     "value": 50
  11.   },
  12.   {
  13.     "_id": ObjectId("5a934e000102030405000002"),
  14.     "date": NumberLong(1648269508044),
  15.     "value": 23
  16.   },
  17.   {
  18.     "_id": ObjectId("5a934e000102030405000003"),
  19.     "date": NumberLong(1648269508044),
  20.     "value": 199
  21.   }
  22. ]

Now, the question is, how to do this with the fluent aggregation API in C#?

答案1

得分: 0

方法1: 将聚合查询作为BsonDocument传递。

  1. var pipelineDefinition = new BsonDocument[]
  2. {
  3.     new BsonDocument
  4.     {
  5.         {
  6.             "$project", new BsonDocument
  7.             {
  8.                 { "date", new BsonDocument { { "$toLong", "$date" } } },
  9.                 { "value", 1 }
  10.             }
  11.         }
  12.     }
  13. };
  15. List<Model> result = _collection.Aggregate<Model>(pipelineDefinition)
  16.     .ToList();

方法2: 使用BsonSerializer。

  1. 实现IBsonSerializer类以将DateTime类型转换为long类型。
  1. public class DateToLongConverter : IBsonSerializer<long>
  2. {
  3.     public Type ValueType => typeof(long);
  5.     public long Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
  6.     {
  7.         var bsonReader = context.Reader;
  8.         return bsonReader.ReadDateTime();
  9.     }
  11.     public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, long value)
  12.     {
  13.         var bsonWriter = context.Writer;
  14.         bsonWriter.WriteInt64(value);
  15.     }
  17.     public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value)
  18.     {
  19.         var bsonWriter = context.Writer;
  20.         bsonWriter.WriteInt64((long)value);
  21.     }
  23.     object IBsonSerializer.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
  24.     {
  25.         var bsonReader = context.Reader;
  26.         return bsonReader.ReadDateTime();
  27.     }
  28. }
  1. 在Date属性上应用BsonSerializer属性，使用DateToLongConverter。
  1. public class Model
  2. {
  3.     public ObjectId Id { get; set; }
  4.     [BsonSerializer(typeof(DateToLongConverter))]
  5.     public long Date { get; set; }
  6.     public int Value { get; set; }
  7. }
  1. 为Model类注册类映射。
  1. BsonClassMap.RegisterClassMap<Model>(cm =>
  2. {
  3.     cm.AutoMap();
  5.     cm.MapMember(x => x.Date)
  6.         .SetSerializer(new DateToLongConverter());
  7. });
  1. 查询数据：
  1. List<Model> result = (await _collection.FindAsync(new BsonDocument()))
  2.     .ToList();

演示

使用 `$toLong` 在 MongoDB C# 查询中

英文:

Approach 1: Pass aggregation query as BsonDocument.

  1. var pipelineDefinition = new BsonDocument[]
  2. {
  3.     new BsonDocument
  4.     {
  5.         {
  6.             &quot;$project&quot;, new BsonDocument
  7.             {
  8.                 { &quot;date&quot;, new BsonDocument { { &quot;$toLong&quot;, &quot;$date&quot; } } },
  9.                 { &quot;value&quot;, 1 }
  10.             }
  11.         }
  12.     }
  13. };
  15. List&lt;Model&gt; result = _collection.Aggregate&lt;Model&gt;(pipelineDefinition)
  16.     .ToList();

Approach 2: Work with BsonSerializer.

  1. Implement IBsonSerializer class to convert from DateTime type to long type.
  1. public class DateToLongConverter : IBsonSerializer&lt;long&gt;
  2. {
  3.     public Type ValueType =&gt; typeof(long);
  5.     public long Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
  6.     {
  7.         var bsonReader = context.Reader;
  8.         return bsonReader.ReadDateTime();
  9.     }
  11.     public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, long value)
  12.     {
  13.         var bsonWriter = context.Writer;
  14.         bsonWriter.WriteInt64(value);
  15.     }
  17.     public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value)
  18.     {
  19.         var bsonWriter = context.Writer;
  20.         bsonWriter.WriteInt64((long)value);
  21.     }
  23.     object IBsonSerializer.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
  24.     {
  25.         var bsonReader = context.Reader;
  26.         return bsonReader.ReadDateTime();
  27.     }
  28. }
  1. Apply BsonSerializer attribute with DateToLongConverter to Date property.
  1. public class Model
  2. {
  3.     public ObjectId Id { get; set; }
  4.     [BsonSerializer(typeof(DateToLongConverter))]
  5.     public long Date { get; set; }
  6.     public int Value { get; set; }
  7. }
  1. Register class map for Model class.
  1. BsonClassMap.RegisterClassMap&lt;Model&gt;(cm =&gt;
  2. {
  3.     cm.AutoMap();
  5.     cm.MapMember(x =&gt; x.Date)
  6.         .SetSerializer(new DateToLongConverter());
  7. });
  1. To query data:
  1. List&lt;Model&gt; result = (await _collection.FindAsync(new BsonDocument()))
  2.     .ToList();

> Demo

使用 `$toLong` 在 MongoDB C# 查询中

huangapple
  • 本文由 发表于 2023年3月7日 15:30:05
  • 转载请务必保留本文链接：https://go.coder-hub.com/75659073.html
  • c#
  • mongodb
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