如何用phantom-dsl增加Cassandra Counter Column？

Question

在phantom-dsl中是否有任何實施計數器操作的例子？

有檢查：

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

均田尋找這個信息的幻象DSL版本：

https://github.com/Netflix/astyanax/wiki/Working-with-counter-columns

---

以下是部分實現。它提出了兩個問題：

1. 我不知道如何從應用程序中獲取值並在計數器表的計數器列中實現增量計數器操作。

2. 如何更新表中與表格中具有不同行數和鍵數的相同條目相關的行。

在thiagos example這兩個表; '歌曲'&'songs_by_artist'都具有相同的行但具有不同的分區（主鍵/集羣列）

我不知道如何在phantom-dsl中更新與相同條目有關的行，例如「記錄「&」record_transaction_counts「表格。

例如

RecordTransactionCounts.{hash, time} relates to Records.{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) 

Answer 1

正如Thiago所建議的那樣，您可以使用+=或者-=運算符來遞減計數器的值。您也可以分別使用increment或decrement方法來實現相同的目的。

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() 
} 

要減小，只需更換行：

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

之前依靠櫃檯太多了，你應該也是谷歌了一下，找到了問題的其他人都遇到過什麼。

Answer 2

爲了在幻象DSL使用CounterColumn，你必須使用下面的模式來增加它：

.modify(_.myCounterColumn += 1) //or whatever value you want to increment 

在你ConcreteRecordTransactionCountsModel你可以改變您的商店以這樣的適當方式增加計數器：

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

我會嘗試更新我的github以及之前工作過的更多示例。如果您有任何建議，請打開一張票，我會這樣做。