Every time I try to create a new table in cassandra with a new TableDef
I end up with a clustering order of ascending and I'm trying to get descending.
I'm using Cassandra 2.1.10, Spark 1.5.1, and Datastax Spark Cassandra Connector 1.5.0-M2.
I'm creating a new TableDef
val table = TableDef("so", "example",
Seq(ColumnDef("parkey", PartitionKeyColumn, TextType)),
Seq(ColumnDef("ts", ClusteringColumn(0), TimestampType)),
Seq(ColumnDef("name", RegularColumn, TextType)))
rdd.saveAsCassandraTableEx(table, SomeColumns("key", "time", "name"))
What I'm expecting to see in Cassandra is
CREATE TABLE so.example (
parkey text,
ts timestamp,
name text,
PRIMARY KEY ((parkey), ts)
) WITH CLUSTERING ORDER BY (ts DESC);
What I end up with is
CREATE TABLE so.example (
parkey text,
ts timestamp,
name text,
PRIMARY KEY ((parkey), ts)
) WITH CLUSTERING ORDER BY (ts ASC);
How can I force it to set the clustering order to descending?
I was not able to find a direct way of doing this. Additionally there are a lot of other options you may want to specify. I ended up extending ColumnDef
and TableDef
and overriding the cql
method in TableDef
. An example of the solution I came up with is below. If someone has a better way or this becomes natively supported I'd be happy to change the answer.
// Scala Enum
object ClusteringOrder {
abstract sealed class Order(val ordinal: Int) extends Ordered[Order]
with Serializable {
def compare(that: Order) = that.ordinal compare this.ordinal
def toInt: Int = this.ordinal
}
case object Ascending extends Order(0)
case object Descending extends Order(1)
def fromInt(i: Int): Order = values.find(_.ordinal == i).get
val values = Set(Ascending, Descending)
}
// extend the ColumnDef case class to add enum support
class ColumnDefEx(columnName: String, columnRole: ColumnRole, columnType: ColumnType[_],
indexed: Boolean = false, val clusteringOrder: ClusteringOrder.Order = ClusteringOrder.Ascending)
extends ColumnDef(columnName, columnRole, columnType, indexed)
// Mimic the ColumnDef object
object ColumnDefEx {
def apply(columnName: String, columnRole: ColumnRole, columnType: ColumnType[_],
indexed: Boolean, clusteringOrder: ClusteringOrder.Order): ColumnDef = {
new ColumnDefEx(columnName, columnRole, columnType, indexed, clusteringOrder)
}
def apply(columnName: String, columnRole: ColumnRole, columnType: ColumnType[_],
clusteringOrder: ClusteringOrder.Order = ClusteringOrder.Ascending): ColumnDef = {
new ColumnDefEx(columnName, columnRole, columnType, false, clusteringOrder)
}
// copied from ColumnDef object
def apply(column: ColumnMetadata, columnRole: ColumnRole): ColumnDef = {
val columnType = ColumnType.fromDriverType(column.getType)
new ColumnDefEx(column.getName, columnRole, columnType, column.getIndex != null)
}
}
// extend the TableDef case class to override the cql method
class TableDefEx(keyspaceName: String, tableName: String, partitionKey: Seq[ColumnDef],
clusteringColumns: Seq[ColumnDef], regularColumns: Seq[ColumnDef], options: String)
extends TableDef(keyspaceName, tableName, partitionKey, clusteringColumns, regularColumns) {
override def cql = {
val stmt = super.cql
val ordered = if (clusteringColumns.size > 0)
s"$stmt\r\nWITH CLUSTERING ORDER BY (${clusteringColumnOrder(clusteringColumns)})"
else stmt
appendOptions(ordered, options)
}
private[this] def clusteringColumnOrder(clusteringColumns: Seq[ColumnDef]): String =
clusteringColumns.map { col =>
col match {
case c: ColumnDefEx => if (c.clusteringOrder == ClusteringOrder.Descending)
s"${c.columnName} DESC" else s"${c.columnName} ASC"
case c: ColumnDef => s"${c.columnName} ASC"
}
}.toList.mkString(", ")
private[this] def appendOptions(stmt: String, opts: String) =
if (stmt.contains("WITH") && opts.startsWith("WITH")) s"$stmt\r\nAND ${opts.substring(4)}"
else if (!stmt.contains("WITH") && opts.startsWith("AND")) s"WITH ${opts.substring(3)}"
else s"$stmt\r\n$opts"
}
// Mimic the TableDef object but return new TableDefEx
object TableDefEx {
def apply(keyspaceName: String, tableName: String, partitionKey: Seq[ColumnDef],
clusteringColumns: Seq[ColumnDef], regularColumns: Seq[ColumnDef], options: String = "") =
new TableDefEx(keyspaceName, tableName, partitionKey, clusteringColumns, regularColumns,
options)
def fromType[T: ColumnMapper](keyspaceName: String, tableName: String): TableDef =
implicitly[ColumnMapper[T]].newTable(keyspaceName, tableName)
}
This allowed me to create new tables in this manner:
val table = TableDefEx("so", "example",
Seq(ColumnDef("parkey", PartitionKeyColumn, TextType)),
Seq(ColumnDefEx("ts", ClusteringColumn(0), TimestampType, ClusteringOrder.Descending)),
Seq(ColumnDef("name", RegularColumn, TextType)))
rdd.saveAsCassandraTableEx(table, SomeColumns("key", "time", "name"))