如何用phantom-dsl增加Cassandra计数器列？ [英] How to increment Cassandra Counter Column with phantom-dsl?

问题描述

是否有在phantom-dsl中实现计数器操作的示例？

Are there any examples of implementing the counter operation within phantom-dsl?

已检查：

http://outworkers.com/blog/post / a-series-on-cassandra-part-3-advanced-features

https://github.com/outworkers/phantom/wiki/Counter-columns

https ：//github.com/outworkers/phantom/blob/develop/phantom-dsl/src/test/scala/com/websudos/phantom/tables/CounterTableTest.scala

Kinda正在寻找此信息的幻影单反版本：

Kinda looking for a phantom-dsl version of this info:

https://github.com/Netfl ix / astyanax / wiki /与专栏合作

以下是部分实现。它提出了两个问题：

The following is a partial implementation. It has risen two questions:

1. 我不确定如何从应用程序中获取值并在其中实现增量计数器操作

1. I am not sure how to take values from within the application and implement the increment counter operation in a counter column within a counter table.

如何更新表中与同一条目相关的行，其中表具有不同的行数和键数。

How to update Rows within tables relating to the same entry where the tables have different number of rows and keys.

在 thiagos example 这两个表； 歌曲和 songs_by_artist都具有相同的行，但具有不同的分区（主键/群集列）

In thiagos example the two tables; 'songs' & 'songs_by_artist' both have the same rows but with different partitions (primary keys / clustering columns)

我不确定在phantom-dsl中如何更新与相同的条目，例如带有记录&下面的 record_transaction_counts表。

I am not sure how in phantom-dsl one would update rows relating to the same entries, such as with "records" & "record_transaction_counts" tables below.

例如

RecordTransactionCounts。{hash，time}与记录有关。{hash，time}

case class Record(hash: String,
                 size: Int,
                 time: Long,
                 difficulty: Float)


sealed class RecordsModel extends CassandraTable[RecordsModel, Record] {

  override def fromRow(row: Row): Record = {
    Record(
      hash(row),
      size(row),
      time(row),
      difficulty(row)
    )
  }

  object hash extends StringColumn(this) with PartitionKey[String]

  object size extends IntColumn(this)

  object time extends LongColumn(this)

  object difficulty extends FloatColumn(this)

}

abstract class ConcreteRecordsModel extends RecordsModel with RootConnector {

  override val tableName = "records"

  def insertNew(block: Record): Future[ResultSet] = insertNewRecord(block).future()

  def insertNewRecord(r: Record) = {
    insert
      .value(_.hash, r.hash)
      .value(_.size, r.size)
      .value(_.time, r.time)
      .value(_.difficulty, r.difficulty)
  }

}

case class RecordTransactionCounts(hash: String, time: Long, num_transactions: Long )

class RecordTransactionCountsModel extends CassandraTable[RecordTransactionCountsModel, RecordTransactionCounts] {

  override def tableName: String = "record_transaction_counts"

  object hash extends StringColumn(this) with PartitionKey[String]

  object time extends LongColumn(this) with ClusteringOrder[Long]

  object num_transactions extends CounterColumn(this)

  override def fromRow(r: Row): RecordTransactionCounts = {
    RecordTransactionCounts(
      hash(r),
      time(r),
      num_transactions(r)
    )
  }

}

abstract class ConcreteRecordTransactionCountsModel extends TransactionCountsModel with RootConnector {

  def createTable(): Future[ResultSet] = {
    create.ifNotExists().future()
  }

  def store(count: RecordTransactionCounts): Future[ResultSet] = {
    insert
      .value(_.hash, count.hash)
      .value(_.time, count.time)
      .value(_.num_transactions, count.num_transactions)
      .future()
  }

  def getCount(hash: String): Future[Option[Long]] = {
    select(_.count).where(_.hash eqs hash).one()
  }
}

class Database(val keyspace: KeySpaceDef) extends DatabaseImpl(keyspace) {

  def insertRecordTransactionCounts(tc: RecordTransactionCounts) = {
    Batch.logged
      .add(ChainDatabase.tc.store(tc))
      .future()
  }

  object tc extends ConcreteRecordTransactionCountsModel with keyspace.Connector

}

object ChainDatabase extends Database(Config.keySpaceDefinition)

推荐答案

如Thiago所建议，则可以使用 + = 或-= 运算符减少计数器的值。您也可以分别使用递增或递减方法来实现相同的目的。

As Thiago suggested, you can use the += or alternatively the -= operator to decrement the value of a counter. You can also use the increment or decrement methods respectively to achieve the same thing.

def increment(count: RecordTransactionCounts): Future[ResultSet] = {
  update
    .where(_.hash eqs count.hash)
    .and(_.time eqs count.time)
    .modify(_.num_transactions += count.num_transactions)
    .future()
}
// or
def increment(count: RecordTransactionCounts): Future[ResultSet] = {
  update
    .where(_.hash eqs count.hash)
    .and(_.time eqs count.time)
    .modify(_.num_transactions increment count.num_transactions)
    .future()
}

要减少，只需将行替换为：

To decrement, simply replace the lines with:

    ...
    .modify(_.num_transactions -= count.num_transactions)
    // or
    .modify(_.num_transactions decrement count.num_transactions)

在您过度依赖柜台之前，y ou还应该让Google找出其他人遇到的问题。

Before you rely too much on counters, you should also Google a bit to find out what problems other people have encountered.

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