public override AstNode Visit(AstNode node)
{
if (!(node is ExpressionNode))
{
// Non-expressions are visited as usual.
return(base.Visit(node));
}
// First, we only visit expressions that contain a subquery.
//
// For correct handling of ProbeColumn we to decect whether probing
// is required or not. Probing is only needed if the existance subquery
// appears in an expression that is not a logical AND or logical OR (or
// an existence subquery itself).
if (AstUtil.ContainsSubselect(node))
{
BinaryExpression binaryExpression = node as BinaryExpression;
bool isLogicalLink = binaryExpression != null &&
(binaryExpression.Op == BinaryOperator.LogicalAnd ||
binaryExpression.Op == BinaryOperator.LogicalOr);
bool isExistenceSubquery = node.NodeType == AstNodeType.AllAnySubselect ||
node.NodeType == AstNodeType.ExistsSubselect;
bool requiresProbing = !isLogicalLink && !isExistenceSubquery;
if (requiresProbing)
{
_probingEnabledStack.Push(true);
}
AstNode resultExpression = base.Visit(node);
if (requiresProbing)
{
_probingEnabledStack.Pop();
}
return(resultExpression);
}
// Don't visit expressions that do not contain suqueries.
return(node);
}
public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
if (node.Predicate == null || !AstUtil.ContainsSubselect(node.Predicate))
{
return(base.VisitJoinAlgebraNode(node));
}
node.Left = VisitAlgebraNode(node.Left);
node.Right = VisitAlgebraNode(node.Right);
switch (node.Op)
{
case JoinAlgebraNode.JoinOperator.InnerJoin:
{
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Predicate = node.Predicate;
filterAlgebraNode.Input = node;
node.Predicate = null;
SetLastAlgebraNode(node);
_probingEnabledStack.Push(false);
filterAlgebraNode.Predicate = VisitExpression(filterAlgebraNode.Predicate);
_probingEnabledStack.Pop();
filterAlgebraNode.Input = GetAndResetLastNode();
return(filterAlgebraNode);
}
case JoinAlgebraNode.JoinOperator.LeftOuterJoin:
{
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Predicate = node.Predicate;
filterAlgebraNode.Input = node.Right;
node.Right = filterAlgebraNode;
node.Predicate = null;
SetLastAlgebraNode(filterAlgebraNode.Input);
_probingEnabledStack.Push(false);
filterAlgebraNode.Predicate = VisitExpression(filterAlgebraNode.Predicate);
_probingEnabledStack.Pop();
filterAlgebraNode.Input = GetAndResetLastNode();
return(node);
}
case JoinAlgebraNode.JoinOperator.RightOuterJoin:
{
node.Op = JoinAlgebraNode.JoinOperator.LeftOuterJoin;
AlgebraNode oldLeft = node.Left;
node.Left = node.Right;
node.Right = oldLeft;
goto case JoinAlgebraNode.JoinOperator.LeftOuterJoin;
}
case JoinAlgebraNode.JoinOperator.FullOuterJoin:
// TODO: Support subqueries in FULL OUTER JOIN.
throw ExceptionBuilder.InternalError("FULL OUTER JOIN containing a subselect predicate in ON clause is not supported.");
default:
throw ExceptionBuilder.UnhandledCaseLabel(node.Op);
}
}
public override ExpressionNode VisitBinaryExpression(BinaryExpression expression)
{
if (expression.Op != BinaryOperator.LogicalAnd &&
expression.Op != BinaryOperator.LogicalOr)
{
return(base.VisitBinaryExpression(expression));
}
if (expression.Op == BinaryOperator.LogicalAnd)
{
// AND
expression.Left = VisitExpression(expression.Left);
expression.Right = VisitExpression(expression.Right);
return(expression);
}
else
{
// OR
AlgebraNode input = GetAndResetLastNode();
_probingEnabledStack.Push(false);
List <ExpressionNode> scalarOrParts = new List <ExpressionNode>();
List <AlgebraNode> algebrizedOrParts = new List <AlgebraNode>();
foreach (ExpressionNode orPart in AstUtil.SplitCondition(LogicalOperator.Or, expression))
{
if (!AstUtil.ContainsSubselect(orPart))
{
scalarOrParts.Add(orPart);
}
else
{
ExpressionNode replacedOrPart = VisitExpression(orPart);
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Input = GetAndResetLastNode();
filterAlgebraNode.Predicate = replacedOrPart;
algebrizedOrParts.Add(filterAlgebraNode);
}
}
if (scalarOrParts.Count > 0)
{
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Predicate = AstUtil.CombineConditions(LogicalOperator.Or, scalarOrParts);
filterAlgebraNode.Input = CreateConstantScan();
algebrizedOrParts.Insert(0, filterAlgebraNode);
}
_probingEnabledStack.Pop();
ConcatAlgebraNode concat = new ConcatAlgebraNode();
concat.DefinedValues = new UnitedValueDefinition[0];
concat.Inputs = algebrizedOrParts.ToArray();
RowBufferEntry probeColumn = CreateProbeColumn();
JoinAlgebraNode leftSemiJoinBetweenInputAndConcat = new JoinAlgebraNode();
leftSemiJoinBetweenInputAndConcat.Op = JoinAlgebraNode.JoinOperator.LeftSemiJoin;
leftSemiJoinBetweenInputAndConcat.PassthruPredicate = CurrentPassthruPredicate;
leftSemiJoinBetweenInputAndConcat.ProbeBufferEntry = probeColumn;
leftSemiJoinBetweenInputAndConcat.Left = input;
leftSemiJoinBetweenInputAndConcat.Right = concat;
SetLastAlgebraNode(leftSemiJoinBetweenInputAndConcat);
return(CreateProbeColumnRef(probeColumn));
}
}