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Version: 2.x

Low Level API

The low level API provides low level query creation and execution while still offering a large reduction in boilerplate. It's is based one to one on DynamoDB abstractions and the surface area consists of:

  • AttrMap which is a convenience container with automatic conversion between Scala values and AttributeValue's. It also has type aliases of PrimaryKey and Item (see reference section for more details)
  • $ function for creating untyped ProjectionExpressions eg $("person.address.houseNumber")
  • query methods in the DynamoDBQuery companion object that all contain the word Item such as getItem, putItem, updateItem, deleteItem, queryAllItem.
  • Expressions - most of these query methods take expressions as arguments. Once we have a ProjectionExpression via the dollar function we can use it as a springboard to create further expressions such as ConditionExpression, UpdateExpression and PrimaryKeyExpression:
    • ConditionExpression's - $("name") === "John"
    • UpdateExpression's - $("name").set("Smith")

Examples of low level queries are shown below:

for {
  _ <- DynamoDBQuery.putItem("person-table", Item("id" -> "1", "name" -> "John", "age" -> 42)).execute
  maybeFound <- DynamoDBQuery.getItem("person-table")(PrimaryKey("id" -> "1")).execute
  _ <- DynamoDBQuery.updateItem("person-table")(PrimaryKey("id" -> "1"))($("name").set("Smith") + $("age").set(21)).execute
  _ <- DynamoDBQuery.deleteItem("person-table")(PrimaryKey("id" -> "1")).execute
} yield ()

However there are some caveats to using the Low Level API:

  • It is not type safe - subtle runtime errors can occur - for example if there are typos in the field names, or if incompatible types are used in expressions.
  • Serialization and deserialization of case classes is the responsibility of the user - this is usually a major burden.