How to use ScalaQuery to insert a BLOB field? - sql

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)