/// <summary>
/// Rewrite a NavigateOp subtree.
/// We call RewriteNavigateOp to return a subtree (and an optional outputVar).
/// If the outputVar is null, then we simply return the subtree produced by those calls.
/// Otherwise, we add the subtree to the "parent" relop (to be outer-applied), and then use the outputVar
/// in its place.
///
/// As an example,
/// select navigate(e) from T
/// gets rewritten into
/// select v from T OuterApply X
/// where X is the subtree returned from the RewriteXXX calls, and "v" is the output var produced by X
///
/// </summary>
/// <param name="op">the navigateOp</param>
/// <param name="n">the navigateOp subtree</param>
/// <returns>the rewritten tree</returns>
public override Node Visit(NavigateOp op, Node n)
{
VisitScalarOpDefault(op, n);
Var outputVar;
var ret = RewriteNavigateOp(n, op, out outputVar);
ret = VisitNode(ret);
// Move subquery to parent relop if necessary
if (outputVar != null)
{
ret = AddSubqueryToParentRelOp(outputVar, ret);
}
return ret;
}
private Node RewriteNavigateOp(Node navigateOpNode, NavigateOp navigateOp, out Var outputVar)
{
outputVar = null;
//
// Currently, navigation of composition relationships is not supported.
//
if (!Helper.IsAssociationType(navigateOp.Relationship))
{
throw new NotSupportedException(Strings.Cqt_RelNav_NoCompositions);
}
//
// If the input to the navigateOp is a GetEntityRefOp, and the navigation
// is to the 1-end of the relationship, convert this into a RelPropertyOp instead - operating on the
// input child to the GetEntityRefOp
//
if (navigateOpNode.Child0.Op.OpType == OpType.GetEntityRef
&&
(navigateOp.ToEnd.RelationshipMultiplicity == RelationshipMultiplicity.ZeroOrOne ||
navigateOp.ToEnd.RelationshipMultiplicity == RelationshipMultiplicity.One))
{
PlanCompiler.Assert(
m_command.IsRelPropertyReferenced(navigateOp.RelProperty),
"Unreferenced rel property? " + navigateOp.RelProperty);
Op relPropertyOp = m_command.CreateRelPropertyOp(navigateOp.RelProperty);
var relPropertyNode = m_command.CreateNode(
relPropertyOp,
navigateOpNode.Child0.Child0);
return relPropertyNode;
}
var relationshipSets = GetRelationshipSets(navigateOp.Relationship);
//
// Special case: when no relationshipsets can be found. Return NULL or an empty multiset,
// depending on the multiplicity of the toEnd
//
if (relationshipSets.Count == 0)
{
//
// If we're navigating to the 1-end of the relationship, then simply return a null constant
//
if (navigateOp.ToEnd.RelationshipMultiplicity
!= RelationshipMultiplicity.Many)
{
return m_command.CreateNode(m_command.CreateNullOp(navigateOp.Type));
}
else // return an empty set
{
return m_command.CreateNode(m_command.CreateNewMultisetOp(navigateOp.Type));
}
}
//
// Build up a UNION-ALL ladder over all the relationshipsets
//
var scanTableNodes = new List<Node>();
var scanTableVars = new List<Var>();
foreach (var relSet in relationshipSets)
{
var tableMD = Command.CreateTableDefinition(relSet);
var tableOp = m_command.CreateScanTableOp(tableMD);
var branchNode = m_command.CreateNode(tableOp);
var branchVar = tableOp.Table.Columns[0];
scanTableVars.Add(branchVar);
scanTableNodes.Add(branchNode);
}
Node unionAllNode = null;
Var unionAllVar;
m_command.BuildUnionAllLadder(scanTableNodes, scanTableVars, out unionAllNode, out unionAllVar);
//
// Now build up the predicate
//
var targetEnd = m_command.CreateNode(
m_command.CreatePropertyOp(navigateOp.ToEnd),
m_command.CreateNode(m_command.CreateVarRefOp(unionAllVar)));
var sourceEnd = m_command.CreateNode(
m_command.CreatePropertyOp(navigateOp.FromEnd),
m_command.CreateNode(m_command.CreateVarRefOp(unionAllVar)));
var predicateNode = m_command.BuildComparison(OpType.EQ, navigateOpNode.Child0, sourceEnd);
var filterNode = m_command.CreateNode(
m_command.CreateFilterOp(),
unionAllNode, predicateNode);
Var projectVar;
var projectNode = m_command.BuildProject(filterNode, targetEnd, out projectVar);
//
// Finally, some magic about single-valued vs collection-valued ends
//
Node ret;
if (navigateOp.ToEnd.RelationshipMultiplicity
== RelationshipMultiplicity.Many)
{
ret = m_command.BuildCollect(projectNode, projectVar);
}
else
{
ret = projectNode;
outputVar = projectVar;
}
return ret;
}
public override void Visit(NavigateOp op, Node n)
{
VisitScalarOpDefault(op, n);
}
/// <summary>
/// Copies a NavigateOp
/// </summary>
/// <param name="op">the NavigateOp</param>
/// <param name="n">the subtree</param>
/// <returns>a copy of the subtree</returns>
public override Node Visit(NavigateOp op, Node n)
{
return(CopyDefault(m_destCmd.CreateNavigateOp(op.Type, op.RelProperty), n));
}
public virtual void Visit(NavigateOp op, Node n)
{
VisitScalarOpDefault(op, n);
}
// <summary>
// Copies a NavigateOp
// </summary>
// <param name="op"> the NavigateOp </param>
// <param name="n"> the subtree </param>
// <returns> a copy of the subtree </returns>
public override Node Visit(NavigateOp op, Node n)
{
return CopyDefault(m_destCmd.CreateNavigateOp(op.Type, op.RelProperty), n);
}
public override void Visit(NavigateOp op, Node n)
{
VisitScalarOpDefault(op, n);
}
