get

  def get[From: Schema](tableName: String)(
    primaryKeyExpr: KeyConditionExpr.PrimaryKeyExpr[From]
  ): DynamoDBQuery[From, Either[ItemError, From]] = ???

The get operation is used to retrieve an item from a table. The KeyConditionExpr.PrimaryKeyExpr can be created using the ProjectionExpression's in the companion object for model class. It returns an Either[ItemError, From] where ItemError is a sealed trait that that has ValueNotFound and DecodingError instances.

for {
  errorOrPerson <- DynamoDBQuery.get("person")(Person.id.primaryKey === "1").execute
} yield errorOrPerson

Working with get return values

Sometimes working with a Either[ItemError, From] can be a little unwieldy so there are two approaches we can take.

The first approach is to use the ZIO absolve method to push all ItemErrors into the ZIO error channel

import zio.dynamodb.syntax._
for {
  person <- DynamoDBQuery.get("person")(Person.id.primaryKey === "1").execute.absolve
} yield person

However sometimes we wish to treat NotFound as a success case and for this the maybeFound extension method can be imported to push the DecodingError into the ZIO error channel and handle NotFound as a successful operation by using an Option type.

import zio.dynamodb.syntax._
for {
  maybePerson <- DynamoDBQuery.get("person")(Person.id.primaryKey === "1").execute.maybeFound
} yield maybePerson

get query operations

<GET_QUERY>
  .consistency(<ConsistencyMode>)
  .where(<ConditionExpression>)