private CellTreeNode SimplifyTreeByMergingNodes(CellTreeNode rootNode)
{
if (rootNode is LeafCellTreeNode)
{
return(rootNode);
}
rootNode = this.RestructureTreeForMerges(rootNode);
List <CellTreeNode> children = rootNode.Children;
for (int index = 0; index < children.Count; ++index)
{
children[index] = this.SimplifyTreeByMergingNodes(children[index]);
}
bool flag1 = CellTreeNode.IsAssociativeOp(rootNode.OpType);
List <CellTreeNode> cellTreeNodeList = !flag1?CellTreeSimplifier.GroupNonAssociativeLeafChildren(children) : CellTreeSimplifier.GroupLeafChildrenByExtent(children);
OpCellTreeNode opCellTreeNode = new OpCellTreeNode(this.m_viewgenContext, rootNode.OpType);
CellTreeNode node1 = (CellTreeNode)null;
bool flag2 = false;
foreach (CellTreeNode node2 in cellTreeNodeList)
{
if (node1 == null)
{
node1 = node2;
}
else
{
bool flag3 = false;
if (!flag2 && node1.OpType == CellTreeOpType.Leaf && node2.OpType == CellTreeOpType.Leaf)
{
flag3 = this.TryMergeCellQueries(rootNode.OpType, ref node1, node2);
}
if (!flag3)
{
opCellTreeNode.Add(node1);
node1 = node2;
if (!flag1)
{
flag2 = true;
}
}
}
}
opCellTreeNode.Add(node1);
return(opCellTreeNode.AssociativeFlatten());
}
// effects: Simplifies the tree rooted at rootNode and returns a new
// tree -- it ensures that the returned tree has at most one node for
// any particular extent unless the tree has nodes of the same extent
// embedded two leaves below LASJ or LOJ, e.g., if we have a tree
// (where Ni indicates a node for extent i - one Ni can be different
// from anohter Ni:
// [N0 IJ N1] LASJ N0 --> This will not be simplified
// canBooleansOverlap indicates whether an original input cell
// contributes to multiple nodes in this tree, e.g., V1 IJ V2 UNION V2 IJ V3
private CellTreeNode SimplifyTreeByMergingNodes(CellTreeNode rootNode)
{
if (rootNode is LeafCellTreeNode)
{
// View already simple!
return(rootNode);
}
Debug.Assert(
rootNode.OpType == CellTreeOpType.LOJ || rootNode.OpType == CellTreeOpType.IJ ||
rootNode.OpType == CellTreeOpType.FOJ || rootNode.OpType == CellTreeOpType.Union ||
rootNode.OpType == CellTreeOpType.LASJ,
"Only handle these operations");
// Before we apply any rule, check if we can improve the opportunity to
// collapse the nodes
rootNode = RestructureTreeForMerges(rootNode);
var children = rootNode.Children;
Debug.Assert(children.Count > 0, "OpCellTreeNode has no children?");
// Apply recursively
for (var i = 0; i < children.Count; i++)
{
children[i] = SimplifyTreeByMergingNodes(children[i]);
}
// Essentially, we have a node with IJ, LOJ, U or FOJ type that
// has some children. Check if some of the children can be merged
// with one another using the corresponding TM/SP rule
// Ops such as IJ, Union and FOJ are associative, i.e., A op (B
// op C) is the same as (A op B) op C. This is not true for LOJ
// and LASJ
var isAssociativeOp = CellTreeNode.IsAssociativeOp(rootNode.OpType);
if (isAssociativeOp)
{
// Group all the leaf cells of an extent together so that we can
// later simply run through them without running nested loops
// We do not do this for LOJ/LASJ nodes since LOJ (LASJ) is not commutative
// (or associative);
children = GroupLeafChildrenByExtent(children);
}
else
{
children = GroupNonAssociativeLeafChildren(children);
}
// childrenSet keeps track of the children that need to be procesed/partitioned
var newNode = new OpCellTreeNode(m_viewgenContext, rootNode.OpType);
CellTreeNode lastChild = null;
var skipRest = false;
foreach (var child in children)
{
if (lastChild == null)
{
// First time in the loop. Just set lastChild
lastChild = child;
continue;
}
var mergedOk = false;
// try to merge lastChild and child
if (false == skipRest &&
lastChild.OpType == CellTreeOpType.Leaf
&&
child.OpType == CellTreeOpType.Leaf)
{
// Both are cell queries. Can try to merge them
// We do not add lastChild since it could merge
// further. It will be added in a later loop or outside the loop
mergedOk = TryMergeCellQueries(rootNode.OpType, ref lastChild, child);
}
if (false == mergedOk)
{
// No merge occurred. Simply add the previous child as it
// is (Note lastChild will be added in the next loop or if
// the loop finishes, outside the loop
newNode.Add(lastChild);
lastChild = child;
if (false == isAssociativeOp)
{
// LOJ is not associative:
// (P loj PA) loj PO != P loj (PA loj PO). The RHS does not have
// Persons who have orders but no addresses
skipRest = true;
}
}
}
newNode.Add(lastChild);
var result = newNode.AssociativeFlatten();
return(result);
}
// effects: Restructure tree so that it is better positioned for merges
private CellTreeNode RestructureTreeForMerges(CellTreeNode rootNode)
{
var children = rootNode.Children;
if (CellTreeNode.IsAssociativeOp(rootNode.OpType) == false ||
children.Count <= 1)
{
return(rootNode);
}
// If this node's operator is associative and each child's
// operator is also associative, check if there is a common set
// of leaf nodes across all grandchildren
var commonGrandChildren = GetCommonGrandChildren(children);
if (commonGrandChildren == null)
{
return(rootNode);
}
var commonChildOpType = children[0].OpType;
// We do have the structure that we are looking for
// (common op2 gc2) op1 (common op2 gc3) op1 (common op2 gc4) becomes
// common op2 (gc2 op1 gc3 op1 gc4)
// e.g., (A IJ B IJ X IJ Y) UNION (A IJ B IJ Y IJ Z) UNION (A IJ B IJ R IJ S)
// becomes A IJ B IJ ((X IJ Y) UNION (Y IJ Z) UNION (R IJ S))
// From each child in children, get the nodes other than commonGrandChildren - these are gc2, gc3, ...
// Each gc2 must be connected by op2 as before, i.e., ABC + ACD = A(BC + CD)
// All children must be OpCellTreeNodes!
var newChildren = new List <OpCellTreeNode>(children.Count);
foreach (OpCellTreeNode child in children)
{
// Remove all children in child that belong to commonGrandChildren
// All grandChildren must be leaf nodes at this point
var newGrandChildren = new List <LeafCellTreeNode>(child.Children.Count);
foreach (LeafCellTreeNode grandChild in child.Children)
{
if (commonGrandChildren.Contains(grandChild) == false)
{
newGrandChildren.Add(grandChild);
}
}
// In the above example, child.OpType is IJ
Debug.Assert(child.OpType == commonChildOpType);
var newChild = new OpCellTreeNode(
m_viewgenContext, child.OpType,
Helpers.AsSuperTypeList <LeafCellTreeNode, CellTreeNode>(newGrandChildren));
newChildren.Add(newChild);
}
// Connect gc2 op1 gc3 op1 gc4 - op1 is UNION in this
// ((X IJ Y) UNION (Y IJ Z) UNION (R IJ S))
// rootNode.Type is UNION
CellTreeNode remainingNodes = new OpCellTreeNode(
m_viewgenContext, rootNode.OpType,
Helpers.AsSuperTypeList <OpCellTreeNode, CellTreeNode>(newChildren));
// Take the common grandchildren and connect via commonChildType
// i.e., A IJ B
CellTreeNode commonNodes = new OpCellTreeNode(
m_viewgenContext, commonChildOpType,
Helpers.AsSuperTypeList <LeafCellTreeNode, CellTreeNode>(commonGrandChildren));
// Connect both by commonChildType
CellTreeNode result = new OpCellTreeNode(
m_viewgenContext, commonChildOpType,
new[] { commonNodes, remainingNodes });
result = result.AssociativeFlatten();
return(result);
}
// effects: Simplifies the tree rooted at rootNode and returns a new
// tree -- it ensures that the returned tree has at most one node for
// any particular extent unless the tree has nodes of the same extent
// embedded two leaves below LASJ or LOJ, e.g., if we have a tree
// (where Ni indicates a node for extent i - one Ni can be different
// from anohter Ni:
// [N0 IJ N1] LASJ N0 --> This will not be simplified
// canBooleansOverlap indicates whether an original input cell
// contributes to multiple nodes in this tree, e.g., V1 IJ V2 UNION V2 IJ V3
private CellTreeNode SimplifyTreeByMergingNodes(CellTreeNode rootNode)
{
if (rootNode is LeafCellTreeNode)
{ // View already simple!
return rootNode;
}
Debug.Assert(rootNode.OpType == CellTreeOpType.LOJ || rootNode.OpType == CellTreeOpType.IJ ||
rootNode.OpType == CellTreeOpType.FOJ || rootNode.OpType == CellTreeOpType.Union ||
rootNode.OpType == CellTreeOpType.LASJ,
"Only handle these operations");
// Before we apply any rule, check if we can improve the opportunity to
// collapse the nodes
rootNode = RestructureTreeForMerges(rootNode);
List<CellTreeNode> children = rootNode.Children;
Debug.Assert(children.Count > 0, "OpCellTreeNode has no children?");
// Apply recursively
for (int i = 0; i < children.Count; i++)
{
children[i] = SimplifyTreeByMergingNodes(children[i]);
}
// Essentially, we have a node with IJ, LOJ, U or FOJ type that
// has some children. Check if some of the children can be merged
// with one another using the corresponding TM/SP rule
// Ops such as IJ, Union and FOJ are associative, i.e., A op (B
// op C) is the same as (A op B) op C. This is not true for LOJ
// and LASJ
bool isAssociativeOp = CellTreeNode.IsAssociativeOp(rootNode.OpType);
if (isAssociativeOp)
{
// Group all the leaf cells of an extent together so that we can
// later simply run through them without running nested loops
// We do not do this for LOJ/LASJ nodes since LOJ (LASJ) is not commutative
// (or associative);
children = GroupLeafChildrenByExtent(children);
}
else
{
children = GroupNonAssociativeLeafChildren(children);
}
// childrenSet keeps track of the children that need to be procesed/partitioned
OpCellTreeNode newNode = new OpCellTreeNode(m_viewgenContext, rootNode.OpType);
CellTreeNode lastChild = null;
bool skipRest = false;
foreach (CellTreeNode child in children)
{
if (lastChild == null)
{
// First time in the loop. Just set lastChild
lastChild = child;
continue;
}
bool mergedOk = false;
// try to merge lastChild and child
if (false == skipRest && lastChild.OpType == CellTreeOpType.Leaf &&
child.OpType == CellTreeOpType.Leaf)
{
// Both are cell queries. Can try to merge them
// We do not add lastChild since it could merge
// further. It will be added in a later loop or outside the loop
mergedOk = TryMergeCellQueries(rootNode.OpType, ref lastChild, child);
}
if (false == mergedOk)
{
// No merge occurred. Simply add the previous child as it
// is (Note lastChild will be added in the next loop or if
// the loop finishes, outside the loop
newNode.Add(lastChild);
lastChild = child;
if (false == isAssociativeOp)
{
// LOJ is not associative:
// (P loj PA) loj PO != P loj (PA loj PO). The RHS does not have
// Persons who have orders but no addresses
skipRest = true;
}
}
}
newNode.Add(lastChild);
CellTreeNode result = newNode.AssociativeFlatten();
return result;
}
// effects: Restructure tree so that it is better positioned for merges
private CellTreeNode RestructureTreeForMerges(CellTreeNode rootNode)
{
List<CellTreeNode> children = rootNode.Children;
if (CellTreeNode.IsAssociativeOp(rootNode.OpType) == false || children.Count <= 1)
{
return rootNode;
}
// If this node's operator is associative and each child's
// operator is also associative, check if there is a common set
// of leaf nodes across all grandchildren
Set<LeafCellTreeNode> commonGrandChildren = GetCommonGrandChildren(children);
if (commonGrandChildren == null)
{
return rootNode;
}
CellTreeOpType commonChildOpType = children[0].OpType;
// We do have the structure that we are looking for
// (common op2 gc2) op1 (common op2 gc3) op1 (common op2 gc4) becomes
// common op2 (gc2 op1 gc3 op1 gc4)
// e.g., (A IJ B IJ X IJ Y) UNION (A IJ B IJ Y IJ Z) UNION (A IJ B IJ R IJ S)
// becomes A IJ B IJ ((X IJ Y) UNION (Y IJ Z) UNION (R IJ S))
// From each child in children, get the nodes other than commonGrandChildren - these are gc2, gc3, ...
// Each gc2 must be connected by op2 as before, i.e., ABC + ACD = A(BC + CD)
// All children must be OpCellTreeNodes!
List<OpCellTreeNode> newChildren = new List<OpCellTreeNode>(children.Count);
foreach (OpCellTreeNode child in children)
{
// Remove all children in child that belong to commonGrandChildren
// All grandChildren must be leaf nodes at this point
List<LeafCellTreeNode> newGrandChildren = new List<LeafCellTreeNode>(child.Children.Count);
foreach (LeafCellTreeNode grandChild in child.Children)
{
if (commonGrandChildren.Contains(grandChild) == false)
{
newGrandChildren.Add(grandChild);
}
}
// In the above example, child.OpType is IJ
Debug.Assert(child.OpType == commonChildOpType);
OpCellTreeNode newChild = new OpCellTreeNode(m_viewgenContext, child.OpType,
Helpers.AsSuperTypeList<LeafCellTreeNode, CellTreeNode>(newGrandChildren));
newChildren.Add(newChild);
}
// Connect gc2 op1 gc3 op1 gc4 - op1 is UNION in this
// ((X IJ Y) UNION (Y IJ Z) UNION (R IJ S))
// rootNode.Type is UNION
CellTreeNode remainingNodes = new OpCellTreeNode(m_viewgenContext, rootNode.OpType,
Helpers.AsSuperTypeList<OpCellTreeNode, CellTreeNode>(newChildren));
// Take the common grandchildren and connect via commonChildType
// i.e., A IJ B
CellTreeNode commonNodes = new OpCellTreeNode(m_viewgenContext, commonChildOpType,
Helpers.AsSuperTypeList<LeafCellTreeNode, CellTreeNode>(commonGrandChildren));
// Connect both by commonChildType
CellTreeNode result = new OpCellTreeNode(m_viewgenContext, commonChildOpType,
new CellTreeNode[] { commonNodes, remainingNodes });
result = result.AssociativeFlatten();
return result;
}