有在phantom dsl中实现计数器操作的例子吗?
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
有点像在寻找这个信息的虚幻dsl版本:
https://github.com/Netflix/astyanax/wiki/Working-with-counter-columns
以下是部分实现。它提出了两个问题:
-
我不知道如何从应用程序中获取值,并在计数器表中的计数器列中实现递增计数器操作。
-
如何更新与同一条目相关的表中的行,其中表具有不同数量的行和键。
在thiagos的例子中,两个表歌曲'&'songs_by_artist’都有相同的行,但有不同的分区(主键/集群列)
我不确定在phantom dsl中如何更新与相同条目相关的行,例如使用"records"&下面的"record_transaction_counts"表。
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)
正如Thiago所建议的,您可以使用+=
或-=
运算符来递减计数器的值。您也可以分别使用increment
或decrement
方法来实现相同的目的。
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()
}
要递减,只需将行替换为:
...
.modify(_.num_transactions -= count.num_transactions)
// or
.modify(_.num_transactions decrement count.num_transactions)
在你过于依赖计数器之前,你还应该用谷歌搜索一下,看看其他人遇到了什么问题。
为了在phantom dsl中使用CounterColumn
,您必须使用以下模式来递增它:
.modify(_.myCounterColumn += 1) //or whatever value you want to increment
在你的ConcreteRecordTransactionCountsModel
中,你可以改变你的商店,以这样一种适当的方式增加计数器:
def increment(count: RecordTransactionCounts): Future[ResultSet] = {
update
.where(_.hash eqs count.hash)
.and(_.time eqs count.time)
.modify(_.num_transactions += count.num_transactions)
.future()
}
我将尝试用我以前工作过的更多例子来更新我的github。如果你有任何建议,请打开一张票,我会这样做的。