public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
// Reorder
//
// A LSJ (B LOJ C) ---> (A LOJ C) LSJ B (LOJ has no join condition and C produces at most one row)
if (node.Op == JoinAlgebraNode.JoinOperator.LeftSemiJoin ||
node.Op == JoinAlgebraNode.JoinOperator.LeftAntiSemiJoin)
{
JoinAlgebraNode rightChildJoin = node.Right as JoinAlgebraNode;
if (rightChildJoin != null &&
rightChildJoin.Op == JoinAlgebraNode.JoinOperator.LeftOuterJoin &&
rightChildJoin.Predicate == null &&
AstUtil.WillProduceAtMostOneRow(rightChildJoin.Right))
{
node.Right = rightChildJoin.Left;
rightChildJoin.Left = node.Left;
node.Left = rightChildJoin;
return(VisitAlgebraNode(node));
}
}
node.Left = VisitAlgebraNode(node.Left);
node.Right = VisitAlgebraNode(node.Right);
return(node);
}
private AlgebraNode ReturnInputIfItProducesJustOneRow(UnaryAlgebraNode node)
{
node.Input = VisitAlgebraNode(node.Input);
if (AstUtil.WillProduceAtMostOneRow(node.Input))
{
return(node.Input);
}
return(node);
}
public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
ShowPlanElement leftElement = ConvertNode(node.Left);
ShowPlanElement rightElement = ConvertNode(node.Right);
PropertyListBuilder propertyListBuilder = new PropertyListBuilder();
AddRowBufferEntries(propertyListBuilder, Resources.ShowPlanGroupOutputList, node.OutputList);
propertyListBuilder.Write(Resources.ShowPlanKeyLogicalOperator, LogicalOperatorToString(node.Op));
AddStatistics(propertyListBuilder, node.StatisticsIterator);
if (node.Predicate != null)
{
propertyListBuilder.Write(Resources.ShowPlanKeyPredicate, node.Predicate.GenerateSource());
}
if (node.OuterReferences != null && node.OuterReferences.Length > 0)
{
AddRowBufferEntries(propertyListBuilder, Resources.ShowPlanGroupOuterReferences, node.OuterReferences);
}
if (node.ProbeBufferEntry != null)
{
WriteRowBufferEntry(propertyListBuilder, Resources.ShowPlanKeyProbeColumn, node.ProbeBufferEntry);
}
if (node.PassthruPredicate != null)
{
propertyListBuilder.Write(Resources.ShowPlanKeyPassthru, node.PassthruPredicate.GenerateSource());
}
// We give a warning if a join has no predicate and no outer reference.
// In this case the join would simply multiply the other side.
// However, we supppress the warning if any side is known at produce at
// most one row.
if (node.Predicate == null &&
(node.OuterReferences == null || node.OuterReferences.Length == 0) &&
!AstUtil.WillProduceAtMostOneRow(node.Left) &&
!AstUtil.WillProduceAtMostOneRow(node.Right))
{
propertyListBuilder.Write(Resources.ShowPlanKeyWarning, Resources.ShowPlanWarningNoJoinPredicate);
}
IList <ShowPlanProperty> properties = propertyListBuilder.ToList();
ShowPlanElement element = new ShowPlanElement(ShowPlanOperator.NestedLoops, properties, leftElement, rightElement);
_currentElement = element;
return(node);
}
private static ResultAlgebraNode CreateAssertedSubquery(ResultAlgebraNode inputNode)
{
if (AstUtil.WillProduceAtMostOneRow(inputNode))
{
return(inputNode);
}
RowBufferEntry inputEntry = inputNode.OutputList[0];
AggregatedValueDefinition countDefinedValue = new AggregatedValueDefinition();
countDefinedValue.Aggregate = new CountAggregateBinding("COUNT");
countDefinedValue.Aggregator = countDefinedValue.Aggregate.CreateAggregator(typeof(int));
countDefinedValue.Argument = LiteralExpression.FromInt32(0);
RowBufferEntry countDefinedValueEntry = new RowBufferEntry(countDefinedValue.Aggregator.ReturnType);
countDefinedValue.Target = countDefinedValueEntry;
RowBufferEntryExpression anyAggregateArgument = new RowBufferEntryExpression();
anyAggregateArgument.RowBufferEntry = inputEntry;
AggregatedValueDefinition anyDefinedValue = new AggregatedValueDefinition();
anyDefinedValue.Aggregate = new FirstAggregateBinding("ANY");
anyDefinedValue.Aggregator = anyDefinedValue.Aggregate.CreateAggregator(inputEntry.DataType);
anyDefinedValue.Argument = anyAggregateArgument;
RowBufferEntry anyDefinedValueEntry = new RowBufferEntry(inputEntry.DataType);
anyDefinedValue.Target = anyDefinedValueEntry;
AggregateAlgebraNode aggregateAlgebraNode = new AggregateAlgebraNode();
aggregateAlgebraNode.Input = inputNode.Input;
aggregateAlgebraNode.DefinedValues = new AggregatedValueDefinition[] { countDefinedValue, anyDefinedValue };
// CASE WHEN SubqueryCount > 1 THEN 0 ELSE NULL END
ExpressionBuilder expressionBuilder = new ExpressionBuilder();
expressionBuilder.Push(new RowBufferEntryExpression(countDefinedValueEntry));
expressionBuilder.Push(LiteralExpression.FromInt32(1));
expressionBuilder.PushBinary(BinaryOperator.Greater);
ExpressionNode whenExpression = expressionBuilder.Pop();
ExpressionNode thenExpression = LiteralExpression.FromInt32(0);
CaseExpression caseExpression = new CaseExpression();
caseExpression.WhenExpressions = new ExpressionNode[] { whenExpression };
caseExpression.ThenExpressions = new ExpressionNode[] { thenExpression };
expressionBuilder.Push(caseExpression);
ExpressionNode predicate = expressionBuilder.Pop();
AssertAlgebraNode assertAlgebraNode = new AssertAlgebraNode();
assertAlgebraNode.Input = aggregateAlgebraNode;
assertAlgebraNode.Predicate = predicate;
assertAlgebraNode.AssertionType = AssertionType.MaxOneRow;
ResultAlgebraNode resultAlgebraNode = new ResultAlgebraNode();
resultAlgebraNode.Input = assertAlgebraNode;
resultAlgebraNode.OutputList = new RowBufferEntry[] { anyDefinedValueEntry };
resultAlgebraNode.ColumnNames = inputNode.ColumnNames;
return(resultAlgebraNode);
}
