Using Indexes

Scanamo supports scanning and querying global secondary indexes. In the following example, we create and use a table called transport with a hash key of mode and range key of line and a global secondary called colour-index with only a hash key on the colour attribute:

import org.scanamo._
import org.scanamo.syntax._
import org.scanamo.generic.auto._

case class Transport(mode: String, line: String, colour: String)
val transport = Table[Transport]("transport")
val colourIndex = transport.index("colour-index")

val client = LocalDynamoDB.syncClient()
val scanamo = Scanamo(client)
import software.amazon.awssdk.services.dynamodb.model.ScalarAttributeType._

LocalDynamoDB.withTableWithSecondaryIndex(client)("transport", "colour-index")("mode" -> S, "line" -> S)("colour" -> S) {
  val operations = for {
    _ <- transport.putAll(Set(
      Transport("Underground", "Circle", "Yellow"),
      Transport("Underground", "Metropolitan", "Maroon"),
      Transport("Underground", "Central", "Red")))
    maroonLine <- colourIndex.query("colour" === "Maroon")
  } yield maroonLine.toList
  scanamo.exec(operations)
}
// res0: List[Either[DynamoReadError, Transport]] = List(
//   Right(Transport("Underground", "Metropolitan", "Maroon"))
// )