/// <summary>
/// Convert a
/// SingleRowOp(X) => X
/// if X produces at most one row
/// </summary>
/// <param name="context">Rule Processing context</param>
/// <param name="singleRowNode">Current subtree</param>
/// <param name="newNode">transformed subtree</param>
/// <returns>Transformation status</returns>
private static bool ProcessSingleRowOpOverAnything(RuleProcessingContext context, Node singleRowNode, out Node newNode)
{
newNode = singleRowNode;
var trc = (TransformationRulesContext)context;
var childNodeInfo = context.Command.GetExtendedNodeInfo(singleRowNode.Child0);
// If the input to this Op can produce at most one row, then we don't need the
// singleRowOp - simply return the input
if (childNodeInfo.MaxRows
<= RowCount.One)
{
newNode = singleRowNode.Child0;
return true;
}
//
// if the current node is a FilterOp, then try and determine if the FilterOp
// produces one row at most
//
if (singleRowNode.Child0.Op.OpType
== OpType.Filter)
{
var predicate = new Predicate(context.Command, singleRowNode.Child0.Child1);
if (predicate.SatisfiesKey(childNodeInfo.Keys.KeyVars, childNodeInfo.Definitions))
{
childNodeInfo.MaxRows = RowCount.One;
newNode = singleRowNode.Child0;
return true;
}
}
// we couldn't do anything
return false;
}
/// <summary>
/// Split up a predicate into 2 parts - the pushdown and the non-pushdown predicate.
///
/// If the filter node has no external references *and* the "columns" parameter is null,
/// then the entire predicate can be pushed down
///
/// We then compute the set of valid column references - if the "columns" parameter
/// is non-null, this set is used. Otherwise, we get the definitions of the
/// input relop node of the filterOp, and use that.
///
/// We use this list of valid column references to identify which parts of the filter
/// predicate can be pushed down - only those parts of the predicate that do not
/// reference anything beyond these columns are considered for pushdown. The rest are
/// stuffed into the nonPushdownPredicate output parameter
///
/// </summary>
/// <param name="command">Command object</param>
/// <param name="filterNode">the FilterOp subtree</param>
/// <param name="columns">(Optional) List of columns to consider for "pushdown"</param>
/// <param name="nonPushdownPredicateNode">(output) Part of the predicate that cannot be pushed down</param>
/// <returns>part of the predicate that can be pushed down</returns>
private static Node GetPushdownPredicate(Command command, Node filterNode, VarVec columns, out Node nonPushdownPredicateNode)
{
var pushdownPredicateNode = filterNode.Child1;
nonPushdownPredicateNode = null;
var filterNodeInfo = command.GetExtendedNodeInfo(filterNode);
if (columns == null
&& filterNodeInfo.ExternalReferences.IsEmpty)
{
return pushdownPredicateNode;
}
if (columns == null)
{
var inputNodeInfo = command.GetExtendedNodeInfo(filterNode.Child0);
columns = inputNodeInfo.Definitions;
}
var predicate = new Predicate(command, pushdownPredicateNode);
Predicate nonPushdownPredicate;
predicate = predicate.GetSingleTablePredicates(columns, out nonPushdownPredicate);
pushdownPredicateNode = predicate.BuildAndTree();
nonPushdownPredicateNode = nonPushdownPredicate.BuildAndTree();
return pushdownPredicateNode;
}
private void GetSingleTablePredicates(List<VarVec> tableDefinitions,
out List<Predicate> singleTablePredicates, out Predicate otherPredicates)
{
singleTablePredicates = new List<Predicate>();
foreach (VarVec vec in tableDefinitions)
{
singleTablePredicates.Add(new Predicate(m_command));
}
otherPredicates = new Predicate(m_command);
VarVec externalRefs = m_command.CreateVarVec();
foreach (Node part in m_parts)
{
NodeInfo nodeInfo = m_command.GetNodeInfo(part);
bool singleTablePart = false;
for (int i = 0; i < tableDefinitions.Count; i++)
{
VarVec tableColumns = tableDefinitions[i];
if (tableColumns != null)
{
externalRefs.InitFrom(nodeInfo.ExternalReferences);
externalRefs.Minus(tableColumns);
if (externalRefs.IsEmpty)
{
singleTablePart = true;
singleTablePredicates[i].AddPart(part);
break;
}
}
}
if (!singleTablePart)
{
otherPredicates.AddPart(part);
}
}
}
internal Predicate GetJoinPredicates(VarVec leftTableDefinitions, VarVec rightTableDefinitions,
out Predicate otherPredicates)
{
Predicate joinPredicate = new Predicate(m_command);
otherPredicates = new Predicate(m_command);
foreach (Node part in m_parts)
{
Var leftTableVar;
Var rightTableVar;
if (Predicate.IsEquiJoinPredicate(part, leftTableDefinitions, rightTableDefinitions, out leftTableVar, out rightTableVar))
{
joinPredicate.AddPart(part);
}
else
{
otherPredicates.AddPart(part);
}
}
return joinPredicate;
}
/// <summary>
/// Get the set of equi-join columns from this predicate
/// </summary>
/// <param name="leftTableDefinitions"></param>
/// <param name="rightTableDefinitions"></param>
/// <param name="leftTableEquiJoinColumns"></param>
/// <param name="rightTableEquiJoinColumns"></param>
/// <param name="otherPredicates"></param>
internal void GetEquiJoinPredicates(VarVec leftTableDefinitions, VarVec rightTableDefinitions,
out List<Var> leftTableEquiJoinColumns, out List<Var> rightTableEquiJoinColumns,
out Predicate otherPredicates)
{
otherPredicates = new Predicate(m_command);
leftTableEquiJoinColumns = new List<Var>();
rightTableEquiJoinColumns = new List<Var>();
foreach (Node part in m_parts)
{
Var leftTableVar;
Var rightTableVar;
if (IsEquiJoinPredicate(part, leftTableDefinitions, rightTableDefinitions, out leftTableVar, out rightTableVar))
{
leftTableEquiJoinColumns.Add(leftTableVar);
rightTableEquiJoinColumns.Add(rightTableVar);
}
else
{
otherPredicates.AddPart(part);
}
}
}
/// <summary>
/// Partition the current predicate into predicates that only apply
/// to the specified table (single-table-predicates), and others
/// </summary>
/// <param name="tableDefinitions">current columns defined by the table</param>
/// <param name="otherPredicates">non-single-table predicates</param>
/// <returns>single-table-predicates</returns>
internal Predicate GetSingleTablePredicates(VarVec tableDefinitions,
out Predicate otherPredicates)
{
List<VarVec> tableDefinitionList = new List<VarVec>();
tableDefinitionList.Add(tableDefinitions);
List<Predicate> singleTablePredicateList;
GetSingleTablePredicates(tableDefinitionList, out singleTablePredicateList, out otherPredicates);
return singleTablePredicateList[0];
}
/// <summary>
/// Convert Filter(OuterApply(X,Y), p) into
/// Filter(CrossApply(X,Y), p)
/// if "p" is not null-preserving for Y (ie) "p" does not preserve null values from Y
/// </summary>
/// <param name="context">Rule processing context</param>
/// <param name="filterNode">Filter node</param>
/// <param name="newNode">modified subtree</param>
/// <returns>transformation status</returns>
private static bool ProcessFilterOverOuterApply(RuleProcessingContext context, Node filterNode, out Node newNode)
{
newNode = filterNode;
var applyNode = filterNode.Child0;
var applyOp = applyNode.Op;
var applyRightInputNode = applyNode.Child1;
var trc = (TransformationRulesContext)context;
var command = trc.Command;
//
// Check to see if the current predicate preserves nulls for the right table.
// If it doesn't then we can convert the outer apply into a cross-apply,
//
var rightTableNodeInfo = command.GetExtendedNodeInfo(applyRightInputNode);
var predicate = new Predicate(command, filterNode.Child1);
if (!predicate.PreservesNulls(rightTableNodeInfo.Definitions, true))
{
var newApplyNode = command.CreateNode(command.CreateCrossApplyOp(), applyNode.Child0, applyRightInputNode);
var newFilterNode = command.CreateNode(command.CreateFilterOp(), newApplyNode, filterNode.Child1);
newNode = newFilterNode;
return true;
}
return false;
}
private static bool ProcessFilterOverJoin(RuleProcessingContext context, Node filterNode, out Node newNode)
{
newNode = filterNode;
var trc = (TransformationRulesContext)context;
//
// Have we shut off filter pushdown for this node? Return
//
if (trc.IsFilterPushdownSuppressed(filterNode))
{
return false;
}
var joinNode = filterNode.Child0;
var joinOp = joinNode.Op;
var leftInputNode = joinNode.Child0;
var rightInputNode = joinNode.Child1;
var command = trc.Command;
var needsTransformation = false;
//
// If we're dealing with an outer-join, first check to see if the current
// predicate preserves nulls for the right table.
// If it doesn't then we can convert the outer join into an inner join,
// and then continue with the rest of our processing here
//
var rightTableNodeInfo = command.GetExtendedNodeInfo(rightInputNode);
var predicate = new Predicate(command, filterNode.Child1);
if (joinOp.OpType
== OpType.LeftOuterJoin)
{
if (!predicate.PreservesNulls(rightTableNodeInfo.Definitions, true))
{
joinOp = command.CreateInnerJoinOp();
needsTransformation = true;
}
}
var leftTableInfo = command.GetExtendedNodeInfo(leftInputNode);
//
// Check to see if the predicate contains any "single-table-filters". In those
// cases, we could simply push that filter down to the child.
// We can do this for inner joins and cross joins - for both inputs.
// For left-outer joins, however, we can only do this for the left-side input
// Further note that we only want to do the pushdown if it will help us - if
// the join input is a ScanTable (or some other cases), then it doesn't help us.
//
Node leftSingleTablePredicateNode = null;
if (leftInputNode.Op.OpType
!= OpType.ScanTable)
{
var leftSingleTablePredicates = predicate.GetSingleTablePredicates(leftTableInfo.Definitions, out predicate);
leftSingleTablePredicateNode = leftSingleTablePredicates.BuildAndTree();
}
Node rightSingleTablePredicateNode = null;
if ((rightInputNode.Op.OpType != OpType.ScanTable)
&&
(joinOp.OpType != OpType.LeftOuterJoin))
{
var rightSingleTablePredicates = predicate.GetSingleTablePredicates(rightTableNodeInfo.Definitions, out predicate);
rightSingleTablePredicateNode = rightSingleTablePredicates.BuildAndTree();
}
//
// Now check to see if the predicate contains some "join predicates". We can
// add these to the existing join predicate (if any).
// We can only do this for inner joins and cross joins - not for LOJs
//
Node newJoinPredicateNode = null;
if (joinOp.OpType == OpType.CrossJoin
|| joinOp.OpType == OpType.InnerJoin)
{
var joinPredicate = predicate.GetJoinPredicates(leftTableInfo.Definitions, rightTableNodeInfo.Definitions, out predicate);
newJoinPredicateNode = joinPredicate.BuildAndTree();
}
//
// Now for the dirty work. We've identified some predicates that could be pushed
// into the left table, some predicates that could be pushed into the right table
// and some that could become join predicates.
//
if (leftSingleTablePredicateNode != null)
{
leftInputNode = command.CreateNode(command.CreateFilterOp(), leftInputNode, leftSingleTablePredicateNode);
needsTransformation = true;
}
if (rightSingleTablePredicateNode != null)
{
rightInputNode = command.CreateNode(command.CreateFilterOp(), rightInputNode, rightSingleTablePredicateNode);
needsTransformation = true;
}
// Identify the new join predicate
if (newJoinPredicateNode != null)
{
needsTransformation = true;
if (joinOp.OpType
== OpType.CrossJoin)
{
joinOp = command.CreateInnerJoinOp();
}
else
{
PlanCompiler.Assert(joinOp.OpType == OpType.InnerJoin, "unexpected non-InnerJoin?");
newJoinPredicateNode = PlanCompilerUtil.CombinePredicates(joinNode.Child2, newJoinPredicateNode, command);
}
}
else
{
newJoinPredicateNode = (joinOp.OpType == OpType.CrossJoin) ? null : joinNode.Child2;
}
//
// If nothing has changed, then just return the current node. Otherwise,
// we will loop forever
//
if (!needsTransformation)
{
return false;
}
Node newJoinNode;
//
// Finally build up a new join node
//
if (joinOp.OpType
== OpType.CrossJoin)
{
newJoinNode = command.CreateNode(joinOp, leftInputNode, rightInputNode);
}
else
{
newJoinNode = command.CreateNode(joinOp, leftInputNode, rightInputNode, newJoinPredicateNode);
}
//
// Build up a new filterNode above this join node. But only if we have a filter left
//
var newFilterPredicateNode = predicate.BuildAndTree();
if (newFilterPredicateNode == null)
{
newNode = newJoinNode;
}
else
{
newNode = command.CreateNode(command.CreateFilterOp(), newJoinNode, newFilterPredicateNode);
}
return true;
}