public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
// Check if node only consists of INNER join nodes and simple table reference nodes.
// This algorithm assumes that the table references have been lineraized so that
//
// - JoinedTableReference appear on the LHS only (the last one must be NamedTableReference ovbiviously)
// - NamedTableReference appear on the RHS only
//
// While scanning the node's children we create a list of all JoinedTableReferences and
// NamedTableReferences.
InnerJoinTableExtractor innerJoinTableExtractor = new InnerJoinTableExtractor();
innerJoinTableExtractor.Visit(node);
if (!innerJoinTableExtractor.ConsistsOnlyOfInnerJoinsFiltersAndTables)
{
node.Left = VisitAlgebraNode(node.Left);
node.Right = VisitAlgebraNode(node.Right);
return(node);
}
else
{
TableAlgebraNode[] algebraNodes = innerJoinTableExtractor.GetTableNodes();
Dictionary <TableRefBinding, TableAlgebraNode> tableRefToNodeDictionary = new Dictionary <TableRefBinding, TableAlgebraNode>();
List <TableRefBinding> tableList = new List <TableRefBinding>();
foreach (TableAlgebraNode algebraNode in algebraNodes)
{
tableRefToNodeDictionary.Add(algebraNode.TableRefBinding, algebraNode);
tableList.Add(algebraNode.TableRefBinding);
}
// Create a mapping RowBufferEntry -> ColumnRefBinding
Dictionary <RowBufferEntry, ColumnRefBinding> rowBufferColumnDictionary = new Dictionary <RowBufferEntry, ColumnRefBinding>();
foreach (TableRefBinding tableRefBinding in tableList)
{
foreach (ColumnRefBinding columnRefBinding in tableRefBinding.ColumnRefs)
{
rowBufferColumnDictionary.Add(columnRefBinding.ValueDefinition.Target, columnRefBinding);
}
}
// Create list of all possible join conditions and remaining AND-parts.
List <JoinCondition> joinConditionList = new List <JoinCondition>();
List <ExpressionNode> andPartList = new List <ExpressionNode>();
ExpressionNode filter = AstUtil.CombineConditions(LogicalOperator.And, innerJoinTableExtractor.GetFilters());
foreach (ExpressionNode andPart in AstUtil.SplitCondition(LogicalOperator.And, filter))
{
JoinCondition joinCondition = ConvertToJoinCondition(rowBufferColumnDictionary, andPart);
if (joinCondition != null)
{
joinConditionList.Add(joinCondition);
}
else
{
andPartList.Add(andPart);
}
}
// After creating the list of all join conditions and AND-parts we have all we need to create
// an optimimal join order between all tables of this part of the table tree.
JoinOrder bestJoinOrder = GetBestJoinOrder(tableList.ToArray(), joinConditionList.ToArray(), andPartList.ToArray());
// Get all tables that are introduced by this join order
Dictionary <RowBufferEntry, ColumnValueDefinition> introducedColumns = GetIntroducedColumns(bestJoinOrder);
// Combine AND-part list with all unused join conditions.
andPartList.AddRange(bestJoinOrder.UnusedConditions);
// Now we will re-create this part of the tree using the this join order.
AlgebraNode lastAlgebraNode = null;
for (int joinIndex = 0; joinIndex < bestJoinOrder.Joins.Length; joinIndex++)
{
Join join = bestJoinOrder.Joins[joinIndex];
AlgebraNode tableInput;
TableAlgebraNode tableNode = tableRefToNodeDictionary[join.TableRefBinding];
ExpressionNode tableFilter = ExtractConditionsApplicableToTable(introducedColumns, andPartList, join.TableRefBinding);
if (tableFilter == null)
{
tableInput = tableNode;
}
else
{
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Input = tableNode;
filterAlgebraNode.Predicate = tableFilter;
tableInput = filterAlgebraNode;
}
if (lastAlgebraNode == null)
{
// This was the first one.
lastAlgebraNode = tableInput;
}
else
{
// Not the first one, we can create a join with the current table reference
// and last table reference.
// Get all AND-parts that can be applied to the tables already joined.
// This expression is merged to one condition.
ExpressionNode[] applicableAndParts = GetAndPartsApplicableToJoin(introducedColumns, bestJoinOrder, joinIndex, andPartList, true);
ExpressionNode condition = AstUtil.CombineConditions(LogicalOperator.And, applicableAndParts);
ExpressionNode joinCondition;
if (join.JoinCondition == null)
{
joinCondition = null;
}
else
{
joinCondition = join.JoinCondition.ToExpression();
}
ExpressionNode completeCondition = AstUtil.CombineConditions(LogicalOperator.And, condition, joinCondition);
JoinAlgebraNode joinAlgebraNode = new JoinAlgebraNode();
joinAlgebraNode.Op = JoinAlgebraNode.JoinOperator.InnerJoin;
joinAlgebraNode.Left = lastAlgebraNode;
joinAlgebraNode.Right = tableInput;
joinAlgebraNode.Predicate = completeCondition;
// Next time this newly created join is the last table reference.
lastAlgebraNode = joinAlgebraNode;
}
}
return(lastAlgebraNode);
}
}
public override AlgebraNode VisitJoinAlgebraNode(JoinAlgebraNode node)
{
// Check if node only consists of INNER join nodes and simple table reference nodes.
// This algorithm assumes that the table references have been lineraized so that
//
// - JoinedTableReference appear on the LHS only (the last one must be NamedTableReference ovbiviously)
// - NamedTableReference appear on the RHS only
//
// While scanning the node's children we create a list of all JoinedTableReferences and
// NamedTableReferences.
InnerJoinTableExtractor innerJoinTableExtractor = new InnerJoinTableExtractor();
innerJoinTableExtractor.Visit(node);
if (!innerJoinTableExtractor.ConsistsOnlyOfInnerJoinsFiltersAndTables)
{
node.Left = VisitAlgebraNode(node.Left);
node.Right = VisitAlgebraNode(node.Right);
return node;
}
else
{
TableAlgebraNode[] algebraNodes = innerJoinTableExtractor.GetTableNodes();
Dictionary<TableRefBinding,TableAlgebraNode> tableRefToNodeDictionary = new Dictionary<TableRefBinding, TableAlgebraNode>();
List<TableRefBinding> tableList = new List<TableRefBinding>();
foreach (TableAlgebraNode algebraNode in algebraNodes)
{
tableRefToNodeDictionary.Add(algebraNode.TableRefBinding, algebraNode);
tableList.Add(algebraNode.TableRefBinding);
}
// Create a mapping RowBufferEntry -> ColumnRefBinding
Dictionary<RowBufferEntry, ColumnRefBinding> rowBufferColumnDictionary = new Dictionary<RowBufferEntry, ColumnRefBinding>();
foreach (TableRefBinding tableRefBinding in tableList)
{
foreach (ColumnRefBinding columnRefBinding in tableRefBinding.ColumnRefs)
rowBufferColumnDictionary.Add(columnRefBinding.ValueDefinition.Target, columnRefBinding);
}
// Create list of all possible join conditions and remaining AND-parts.
List<JoinCondition> joinConditionList = new List<JoinCondition>();
List<ExpressionNode> andPartList = new List<ExpressionNode>();
ExpressionNode filter = AstUtil.CombineConditions(LogicalOperator.And, innerJoinTableExtractor.GetFilters());
foreach (ExpressionNode andPart in AstUtil.SplitCondition(LogicalOperator.And, filter))
{
JoinCondition joinCondition = ConvertToJoinCondition(rowBufferColumnDictionary, andPart);
if (joinCondition != null)
joinConditionList.Add(joinCondition);
else
andPartList.Add(andPart);
}
// After creating the list of all join conditions and AND-parts we have all we need to create
// an optimimal join order between all tables of this part of the table tree.
JoinOrder bestJoinOrder = GetBestJoinOrder(tableList.ToArray(), joinConditionList.ToArray(), andPartList.ToArray());
// Get all tables that are introduced by this join order
Dictionary<RowBufferEntry, ColumnValueDefinition> introducedColumns = GetIntroducedColumns(bestJoinOrder);
// Combine AND-part list with all unused join conditions.
andPartList.AddRange(bestJoinOrder.UnusedConditions);
// Now we will re-create this part of the tree using the this join order.
AlgebraNode lastAlgebraNode = null;
for (int joinIndex = 0; joinIndex < bestJoinOrder.Joins.Length; joinIndex++)
{
Join join = bestJoinOrder.Joins[joinIndex];
AlgebraNode tableInput;
TableAlgebraNode tableNode = tableRefToNodeDictionary[join.TableRefBinding];
ExpressionNode tableFilter = ExtractConditionsApplicableToTable(introducedColumns, andPartList, join.TableRefBinding);
if (tableFilter == null)
{
tableInput = tableNode;
}
else
{
FilterAlgebraNode filterAlgebraNode = new FilterAlgebraNode();
filterAlgebraNode.Input = tableNode;
filterAlgebraNode.Predicate = tableFilter;
tableInput = filterAlgebraNode;
}
if (lastAlgebraNode == null)
{
// This was the first one.
lastAlgebraNode = tableInput;
}
else
{
// Not the first one, we can create a join with the current table reference
// and last table reference.
// Get all AND-parts that can be applied to the tables already joined.
// This expression is merged to one condition.
ExpressionNode[] applicableAndParts = GetAndPartsApplicableToJoin(introducedColumns, bestJoinOrder, joinIndex, andPartList, true);
ExpressionNode condition = AstUtil.CombineConditions(LogicalOperator.And, applicableAndParts);
ExpressionNode joinCondition;
if (join.JoinCondition == null)
joinCondition = null;
else
joinCondition = join.JoinCondition.ToExpression();
ExpressionNode completeCondition = AstUtil.CombineConditions(LogicalOperator.And, condition, joinCondition);
JoinAlgebraNode joinAlgebraNode = new JoinAlgebraNode();
joinAlgebraNode.Op = JoinAlgebraNode.JoinOperator.InnerJoin;
joinAlgebraNode.Left = lastAlgebraNode;
joinAlgebraNode.Right = tableInput;
joinAlgebraNode.Predicate = completeCondition;
// Next time this newly created join is the last table reference.
lastAlgebraNode = joinAlgebraNode;
}
}
return lastAlgebraNode;
}
}
