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Version: 2.x

DynamoDB Transactions

Transactions are as simple as calling the .transaction method on a DynamoDBQuery. As long as every component of the query is a valid transaction item and the DynamoDBQuery does not have a mix of get and write transaction items. A list of valid items for both types of queries is listed below.

Examples​

Assuming the below model:

final case class Student(email: String, subject: String)
object Person {
  implicit lazy val schema: Schema.CaseClass2[String, String, Student] = DeriveSchema.gen[Student]

  val (email, subject) = ProjectionExpression.accessors[Student]
}
final case class Bill(email: String, amount: Int)
object Bill {
  implicit lazy val schema: Schema.CaseClass2[String, Int, Bill] = DeriveSchema.gen[Bill]

  val (email, amount) = ProjectionExpression.accessors[Bill]
}
final case class WaitList(email: String)
object Bill {
  implicit lazy val schema: Schema.CaseClass1[String, WaitList] = DeriveSchema.gen[WaitList]

  val email = ProjectionExpression.accessors[WaitList]
}

Write Transactions​

val student = Student("avi@gmail.com", "maths")
val bill = Bill("avi@gmail.com", 1)

val putStudent = put("student", student)
val billedStudent = put("billing", bill)
val deleteFromWaitlist = deleteFrom("waitlist")(WaitList.email.partitionKey === student.email)

val studentEnrollmentTransaction = (putStudent zip billedStudent zip deleteFromWaitlist).transaction

for {
  _ <- studentEnrollmentTransaction.execute
} yield ()

ReadTransactions​

val getStudent = get("student")(Student.id.partitionKey === "1")
val getBill = get("billing")(Bill.id.partitionKey === "1")

val getStudentAndBillTransaction = (getStudent zip getBill).transaction

for {
  studentAndBill <- getStudentAndBillTransaction.execute
} yield studentAndBill

Transaction Failures​

DynamoDBQueries using the .transaction method will fail at runtime if there are invalid transaction actions such as creating a table, scanning for items, or querying. Note a limited number of actions that can be performed for either a read or a write transaction. There is a .safeTransaction method that is also available that will return Either[DynamoDBError.TransactionError, DynamoDBQuery[A]].

There are more examples in our integration tests here and here.

Valid Transact Write Items​

  • PutItem
  • DeleteItem
  • BatchWriteItem
  • UpdateItem
  • ConditionCheck

Valid Transact Get Item​

  • GetItem
  • BatchGetItem