When working with Play Framework, using anorm for the database layer is a common choice, while its a pretty handy library, it doesn’t support lots of custom postgres features, like parsing results that use the citext extension. This post shows how to parse such CITEXT types.

In summary, we need to create a custom column mapper that transforms a PGobject to a String when the object type is citext, which avoids the TypeDoesNotMatch error that is thrown when you try to parse a citext column to a String.

The citext column mapper

This is a way to define the citext column mapper, which needs to be referenced any time you are parsing a citext column:

object CommonParsers {
  import anorm.{Column, MetaDataItem, TypeDoesNotMatch}
  import org.postgresql.util.PGobject

  val citextToString: Column[String] = Column.nonNull {
    case (value, meta) =>
      val MetaDataItem(qualified, _, clazz) = meta
      value match {
        case str: String => Right(str)
        case obj: PGobject if "citext" equalsIgnoreCase obj.getType => Right(obj.getValue)
        case _ =>
          Left(
            TypeDoesNotMatch(
              s"Cannot convert $value: ${value.asInstanceOf[AnyRef].getClass} to String for column $qualified, class = $clazz"
            )
          )
      }
  }
}

Usage

To ilustrate the usage, let’s define a simple table that uses the citext type:

CREATE EXTENSION IF NOT EXISTS CITEXT;

CREATE TABLE users(
  user_id UUID NOT NULL,
  email CITEXT NOT NULL,
  CONSTRAINT users_id_pk PRIMARY KEY (user_id),
);

Proceed to write the query:

object UsersDAO {
  import anorm._

  private val parser = SqlParser.str("email")(CommonParsers.citextToString))

  def getEmails(implicit conn: Connection): List[String] = {
    SQL"""SELECT email FROM users """.as(parser.*)
  }
}

More

The astute reader has noticed that our citextToString mapper knows how to deal with the String type, which allows to define it as a implicit value, which means that if all your parsers have that mapper in scope, you won’t even need to specify when you are expecting a citext type.

The source code for this page can be found here.