public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
node.Left = VisitAlgebraNode(node.Left);
node.Right = VisitAlgebraNode(node.Right);
// Reorder (pull LOJ out of IJ)
//
// (A LOJ B) IJ C ---> (A IJ C) LOJ B (IJ does not depend on B)
// (A ROJ B) IJ C ---> A ROJ (B IJ C) (IJ does not depend on A)
if (node.Op == JoinAlgebraNode.JoinOperator.InnerJoin)
{
JoinAlgebraNode childJoin = node.Left as JoinAlgebraNode;
if (childJoin != null &&
(childJoin.Op == JoinAlgebraNode.JoinOperator.LeftOuterJoin ||
childJoin.Op == JoinAlgebraNode.JoinOperator.RightOuterJoin))
{
if (childJoin.Op == JoinAlgebraNode.JoinOperator.LeftOuterJoin)
{
if (AstUtil.JoinDoesNotDependOn(node, childJoin.Right))
{
node.Left = childJoin.Left;
childJoin.Left = node;
return(VisitAlgebraNode(childJoin));
}
}
else if (childJoin.Op == JoinAlgebraNode.JoinOperator.RightOuterJoin)
{
if (AstUtil.JoinDoesNotDependOn(node, childJoin.Left))
{
node.Left = childJoin.Right;
childJoin.Right = node;
return(VisitAlgebraNode(childJoin));
}
}
}
}
//// Reorder (push LSJ)
////
//// (A J B) LSJ C ---> (A LSJ C) J B (LSJ does not depend on B)
//// (A J B) LSJ C ---> A J (B LSJ C) (LSJ does not depend on A)
//if (node.Op == JoinAlgebraNode.JoinOperator.LeftSemiJoin ||
// node.Op == JoinAlgebraNode.JoinOperator.LeftAntiSemiJoin)
//{
// JoinAlgebraNode childJoin = node.Left as JoinAlgebraNode;
// if (childJoin != null)
// {
// if (AstUtil.JoinDoesNotDependOn(node, childJoin.Right))
// {
// node.Left = childJoin.Left;
// childJoin.Left = node;
// return VisitAlgebraNode(childJoin);
// }
// if (AstUtil.JoinDoesNotDependOn(node, childJoin.Left))
// {
// node.Left = childJoin.Right;
// childJoin.Right = node;
// return VisitAlgebraNode(childJoin);
// }
// }
//}
return(node);
}
