How to use ScalaQuery to insert a BLOB field?

Question

I used ScalaQuery and Scala.

If I have an Array[Byte] object, how do I insert it into the table?

object TestTable extends BasicTable[Test]("test") {
  def id = column[Long]("mid", O.NotNull)
  def extInfo = column[Blob]("mbody", O.Nullable)

  def * = id ~ extInfo <> (Test, Test.unapply _)
}

case class Test(id: Long, extInfo: Blob)

Can I define the method used def extInfo = column[Array[Byte]]("mbody", O.Nullable), how to operate(UPDATE, INSERT, SELECT) with the BLOB type field?

BTW: no ScalaQuery tag

Answer 1

Since the BLOB field is nullable, I suggest changing its Scala type to Option[Blob], for the following definition:

object TestTable extends Table[Test]("test") {
  def id = column[Long]("mid")
  def extInfo = column[Option[Blob]]("mbody")
  def * = id ~ extInfo <> (Test, Test.unapply _)
}

case class Test(id: Long, extInfo: Option[Blob])

You can use a raw, nullable Blob value if you prefer, but then you need to use orElse(null) on the column to actually get a null value out of it (instead of throwing an Exception):

      def * = id ~ extInfo.orElse(null) <> (Test, Test.unapply _)

Now for the actual BLOB handling. Reading is straight-forward: You just get a Blob object in the result which is implemented by the JDBC driver, e.g.:

  Query(TestTable) foreach { t =>
    println("mid=" + t.id + ", mbody = " +
      Option(t.extInfo).map { b => b.getBytes(1, b.length.toInt).mkString })
  }

If you want to insert or update data, you need to create your own BLOBs. A suitable implementation for a stand-alone Blob object is provided by JDBC's RowSet feature:

import javax.sql.rowset.serial.SerialBlob

TestTable insert Test(1, null)
TestTable insert Test(2, new SerialBlob(Array[Byte](1,2,3)))

Edit: And here's a TypeMapper[Array[Byte]] for Postgres (whose BLOBs are not yet supported by ScalaQuery):

  implicit object PostgresByteArrayTypeMapper extends
      BaseTypeMapper[Array[Byte]] with TypeMapperDelegate[Array[Byte]] {
    def apply(p: BasicProfile) = this
    val zero = new Array[Byte](0)
    val sqlType = java.sql.Types.BLOB
    override val sqlTypeName = "BYTEA"
    def setValue(v: Array[Byte], p: PositionedParameters) {
      p.pos += 1
      p.ps.setBytes(p.pos, v)
    }
    def setOption(v: Option[Array[Byte]], p: PositionedParameters) {
      p.pos += 1
      if(v eq None) p.ps.setBytes(p.pos, null) else p.ps.setBytes(p.pos, v.get)
    }
    def nextValue(r: PositionedResult) = {
      r.pos += 1
      r.rs.getBytes(r.pos)
    }
    def updateValue(v: Array[Byte], r: PositionedResult) {
      r.pos += 1
      r.rs.updateBytes(r.pos, v)
    }
    override def valueToSQLLiteral(value: Array[Byte]) =
      throw new SQueryException("Cannot convert BYTEA to literal")
  }

Answer 2

I just post an updated code for Scala and SQ, maybe it will save some time for somebody:

object PostgresByteArrayTypeMapper extends
    BaseTypeMapper[Array[Byte]] with TypeMapperDelegate[Array[Byte]] {
  def apply(p: org.scalaquery.ql.basic.BasicProfile) = this
  val zero = new Array[Byte](0)
  val sqlType = java.sql.Types.BLOB
  override val sqlTypeName = "BYTEA"
  def setValue(v: Array[Byte], p: PositionedParameters) {
    p.pos += 1
    p.ps.setBytes(p.pos, v)
  }
  def setOption(v: Option[Array[Byte]], p: PositionedParameters) {
    p.pos += 1
    if(v eq None) p.ps.setBytes(p.pos, null) else p.ps.setBytes(p.pos, v.get)
  }
  def nextValue(r: PositionedResult) = {
    r.nextBytes()
  }
  def updateValue(v: Array[Byte], r: PositionedResult) {
    r.updateBytes(v)
  }
  override def valueToSQLLiteral(value: Array[Byte]) =
    throw new org.scalaquery.SQueryException("Cannot convert BYTEA to literal")

}

and then usage, for example:

...
// defining a column
def content = column[Array[Byte]]("page_Content")(PostgresByteArrayTypeMapper)