Question

我想计算视频的观看次数。我有以下结构。


package com.test

import java.util
import java.util.concurrent.ExecutorService

import org.apache.hadoop.hbase.client.{Connection, ConnectionFactory, Put, Table}
import org.apache.hadoop.hbase.security.User
import org.apache.hadoop.hbase.{HBaseConfiguration, TableName}
import org.apache.spark.sql.ForeachWriter

import scala.collection.mutable

trait HBaseBulkForeachWriter[RECORD] extends ForeachWriter[RECORD] {

  val tableName: String
  val hbaseConfResources: mutable.Seq[String] = mutable.Seq("location for core-site.xml", "location for hbase-site.xml")

  def pool: Option[ExecutorService] = None

  def user: Option[User] = None

  private var hTable: Table = _
  private var connection: Connection = _

  override def open(partitionId: Long, version: Long): Boolean = {
    connection = createConnection()
    hTable = getHTable(connection)
    true
  }

  def createConnection(): Connection = {
    val hbaseConfig = HBaseConfiguration.create()
    hbaseConfResources.foreach(hbaseConfig.addResource)
    ConnectionFactory.createConnection(hbaseConfig, pool.orNull, user.orNull)
  }

  def getHTable(connection: Connection): Table = {
    connection.getTable(TableName.valueOf(tableName))
  }

  override def process(record: RECORD): Unit = {
    val put = bulkPut
    hTable.put(put)
  }

  override def close(errorOrNull: Throwable): Unit = {
    hTable.close()
    connection.close()
  }

  def bulkPut: util.ArrayList[Put]
}

我只需要计算两个数组（{ _id: ObjectId("some_id") views:[ { userId:1, groupId:[1,2,4] }, { userId:2, groupId:[2,4] }, { userId:1, groupId:[3,5] } ] }和输入数组）是否具有公共元素，请将计数增加一。如果输入数组为views.groupId，则视图数为2。（第一个对象的元素为1，第三个对象的元素为3,5）

我编写了以下代码，但给出了错误的答案。

[1,3,5]

我花了更多时间自己解决问题，但今天没有运气。预先感谢

Answer 1

使用$setIntersection和$size的方法是正确的，但是由于您要将数组转换为单个值，因此最好使用$reduce。另外，使用$min可以确保每次迭代中添加的值分别为1或0（最多1）：

db.collection.aggregate([
    {
        $project: {
            views: {
                $reduce: {
                    input: "$views",
                    initialValue: 0,
                    in: {
                        $add: [
                            "$$value",
                            {
                                $min: [ 1, { $size: { $setIntersection: [ "$$this.groupId", [ 1,3,5 ] ]  } } ]
                            }
                        ]
                    }
                }
            }
        }
    }
])

Mongo Playground

Answer 2

您需要为$filter运算符定义有效条件。

对于您而言，如果您在Number参数中返回cond值，它将用this convention将其转换为Boolean：

db.collection.aggregate([
  {
    $project: {
      views: {
        $size: {
          $ifNull: [
            {
              $filter: {
                input: "$views",
                as: "view",
                cond: {
                  $size: {
                    $setIntersection: [
                      "$$view.groupId",
                      [ 1, 3, 5]
                    ]
                  }
                }
              }
            },
            []
          ]
        }
      }
    }
  }
])

MongoPlayground | Alternative $gt

如果输入数组的元素至少匹配一个，则获取数组的大小

2 个答案: