/// <summary>
/// Utility method that determines whether a given CaseOp subtree can be optimized.
/// Called by both PreProcessor and NominalTypeEliminator.
///
/// If the case statement is of the shape:
/// case when X then NULL else Y, or
/// case when X then Y else NULL,
/// where Y is of row type, and the types of the input CaseOp, the NULL and Y are the same,
/// return true
/// </summary>
/// <param name="op"></param>
/// <param name="n"></param>
/// <returns></returns>
internal static bool IsRowTypeCaseOpWithNullability(CaseOp op, Node n, out bool thenClauseIsNull)
{
thenClauseIsNull = false; //any default value will do
if (!TypeSemantics.IsRowType(op.Type))
{
return false;
}
if (n.Children.Count != 3)
{
return false;
}
//All three types must be equal
if (!n.Child1.Op.Type.EdmEquals(op.Type) || !n.Child2.Op.Type.EdmEquals(op.Type))
{
return false;
}
//At least one of Child1 and Child2 needs to be a null
if (n.Child1.Op.OpType == OpType.Null)
{
thenClauseIsNull = true;
return true;
}
if (n.Child2.Op.OpType == OpType.Null)
{
// thenClauseIsNull stays false
return true;
}
return false;
}
/// <summary>
/// Utility method that determines whether a given CaseOp subtree can be optimized.
/// Called by both PreProcessor and NominalTypeEliminator.
///
/// If the case statement is of the shape:
/// case when X then NULL else Y, or
/// case when X then Y else NULL,
/// where Y is of row type, and the types of the input CaseOp, the NULL and Y are the same,
/// return true
/// </summary>
/// <param name="op"></param>
/// <param name="n"></param>
/// <returns></returns>
internal static bool IsRowTypeCaseOpWithNullability(CaseOp op, Node n, out bool thenClauseIsNull)
{
thenClauseIsNull = false; //any default value will do
if (!TypeSemantics.IsRowType(op.Type))
{
return(false);
}
if (n.Children.Count != 3)
{
return(false);
}
//All three types must be equal
if (!n.Child1.Op.Type.EdmEquals(op.Type) || !n.Child2.Op.Type.EdmEquals(op.Type))
{
return(false);
}
//At least one of Child1 and Child2 needs to be a null
if (n.Child1.Op.OpType == OpType.Null)
{
thenClauseIsNull = true;
return(true);
}
if (n.Child2.Op.OpType == OpType.Null)
{
// thenClauseIsNull stays false
return(true);
}
return(false);
}
private static bool ProcessSimplifyCase(
RuleProcessingContext context,
System.Data.Entity.Core.Query.InternalTrees.Node caseOpNode,
out System.Data.Entity.Core.Query.InternalTrees.Node newNode)
{
CaseOp op = (CaseOp)caseOpNode.Op;
newNode = caseOpNode;
return(ScalarOpRules.ProcessSimplifyCase_Collapse(caseOpNode, out newNode) || ScalarOpRules.ProcessSimplifyCase_EliminateWhenClauses(context, op, caseOpNode, out newNode));
}
public override void Visit(CaseOp op, System.Data.Entity.Core.Query.InternalTrees.Node n)
{
PropertyRefList propertyRefList = this.GetPropertyRefList(n);
for (int index = 1; index < n.Children.Count - 1; index += 2)
{
PropertyRefList propertyRefs = propertyRefList.Clone();
this.AddPropertyRefs(n.Children[index], propertyRefs);
}
this.AddPropertyRefs(n.Children[n.Children.Count - 1], propertyRefList.Clone());
this.VisitChildren(n);
}
internal static bool IsRowTypeCaseOpWithNullability(
CaseOp op,
System.Data.Entity.Core.Query.InternalTrees.Node n,
out bool thenClauseIsNull)
{
thenClauseIsNull = false;
if (!TypeSemantics.IsRowType(op.Type) || n.Children.Count != 3 || (!n.Child1.Op.Type.EdmEquals((MetadataItem)op.Type) || !n.Child2.Op.Type.EdmEquals((MetadataItem)op.Type)))
{
return(false);
}
if (n.Child1.Op.OpType == OpType.Null)
{
thenClauseIsNull = true;
return(true);
}
return(n.Child2.Op.OpType == OpType.Null);
}
/// <summary>
/// CaseOp handling
///
/// Pushes its desired properties to each of the WHEN/ELSE clauses
/// </summary>
/// <param name="op"></param>
/// <param name="n"></param>
public override void Visit(CaseOp op, Node n)
{
// First find the properties that my parent expects from me
PropertyRefList pdProps = GetPropertyRefList(n);
// push down the same properties to my then/else clauses.
// the "when" clauses are irrelevant
for (int i = 1; i < n.Children.Count - 1; i += 2)
{
PropertyRefList cdProps = pdProps.Clone();
AddPropertyRefs(n.Children[i], cdProps);
}
AddPropertyRefs(n.Children[n.Children.Count - 1], pdProps.Clone());
// Now visit the children
VisitChildren(n);
}
public override void Visit(CaseOp op, Node n)
{
VisitScalarOpDefault(op, n);
Assert((n.Children.Count >= 3 && n.Children.Count % 2 == 1),
"CaseOp: Expected odd number of arguments, and at least 3; found {0}", n.Children.Count);
// Validate that each when statement is of type Boolean
for (int i = 0; i < n.Children.Count - 1; i += 2)
{
Assert(TypeSemantics.IsBooleanType(n.Children[i].Op.Type), "Encountered a when node with a non-boolean return type");
}
// Ensure that the then clauses, the else clause and the result type are all the same
for (int i = 1; i < n.Children.Count - 1; i += 2)
{
AssertEqualTypes(n.Op.Type, n.Children[i].Op.Type);
}
AssertEqualTypes(n.Op.Type, n.Children[n.Children.Count - 1].Op.Type);
}
public override void Visit(CaseOp op, Node n)
{
using (new AutoXml(this, op)) {
int i = 0;
while (i < n.Children.Count)
{
if ((i + 1) < n.Children.Count)
{
using (new AutoXml(this, "when")) {
VisitNode(n.Children[i++]);
}
using (new AutoXml(this, "then")) {
VisitNode(n.Children[i++]);
}
}
else
{
using (new AutoXml(this, "else")) {
VisitNode(n.Children[i++]);
}
}
}
}
}
// <summary>
// We don't yet support nest pullups over Case
// </summary>
public override Node Visit(CaseOp op, Node n)
{
// Make sure we don't have a child that is a nest op.
foreach (var chi in n.Children)
{
if (chi.Op.OpType
== OpType.Collect)
{
throw new NotSupportedException(Strings.ADP_NestingNotSupported(op.OpType.ToString(), chi.Op.OpType.ToString()));
}
else if (chi.Op.OpType
== OpType.VarRef)
{
var refVar = ((VarRefOp)chi.Op).Var;
if (m_definingNodeMap.ContainsKey(refVar))
{
throw new NotSupportedException(Strings.ADP_NestingNotSupported(op.OpType.ToString(), chi.Op.OpType.ToString()));
}
}
}
return VisitDefault(n);
}
/// <summary>
/// CaseOp
/// Special handling
/// If the case statement is of one of the following two shapes:
/// (1) case when X then NULL else Y, or
/// (2) case when X then Y else NULL,
/// where Y is of row type and the types of the input CaseOp, the NULL and Y are the same,
/// it gets rewritten into: Y', where Y's null sentinel N' is:
/// (1) case when X then NULL else N, or
/// where N is Y's null sentinel.
/// </summary>
/// <param name="op"> the CaseOp </param>
/// <param name="n"> corresponding node </param>
/// <returns> new subtree </returns>
public override Node Visit(CaseOp op, Node n)
{
// Before visiting the children, check whether the case statment can be optimized
bool thenClauseIsNull;
var canSimplifyPrecheck = PlanCompilerUtil.IsRowTypeCaseOpWithNullability(op, n, out thenClauseIsNull);
VisitChildren(n);
if (canSimplifyPrecheck)
{
Node rewrittenNode;
if (TryRewriteCaseOp(n, thenClauseIsNull, out rewrittenNode))
{
return rewrittenNode;
}
}
//
// If the CaseOp returns a simple type, then we don't need to do
// anything special.
//
// Bug 480780: We must perform further processing, if the result
// type is not a scalar
//
// If the CaseOp returns a collection, then we need to create a
// new CaseOp of the new and improved collection type. Similarly
// for enums we need to convert the result of the operation from
// the enum type to the underlying type of the enum type, and
// for spatial types we must convert it to the underlying spatial union type.
if (TypeUtils.IsCollectionType(op.Type)
|| md.TypeSemantics.IsEnumerationType(op.Type)
|| md.TypeSemantics.IsStrongSpatialType(op.Type))
{
var newType = GetNewType(op.Type);
n.Op = m_command.CreateCaseOp(newType);
return n;
}
else if (TypeUtils.IsStructuredType(op.Type))
{
// We've got a structured type, so the CaseOp is flattened out into
// a NewRecordOp via the FlattenCaseOp method.
var desiredProperties = m_nodePropertyMap[n];
var newNode = FlattenCaseOp(n, m_typeInfo.GetTypeInfo(op.Type), desiredProperties);
return newNode;
}
else
{
return n;
}
}
private static bool ProcessSimplifyCase_EliminateWhenClauses(
RuleProcessingContext context, CaseOp caseOp, Node caseOpNode, out Node newNode)
{
List<Node> newNodeArgs = null;
newNode = caseOpNode;
for (var i = 0; i < caseOpNode.Children.Count;)
{
// Special handling for the else clause
if (i == caseOpNode.Children.Count - 1)
{
// If the else clause is a SoftCast then we do not attempt to simplify
// the case operation, since this may change the result type.
// This really belongs in more general SoftCastOp logic in the CTreeGenerator
// that converts SoftCasts that could affect the result type of the query into
// a real cast or a trivial case statement, to preserve the result type.
// This is tracked by SQL PT Work Item #300003327.
if (OpType.SoftCast
== caseOpNode.Children[i].Op.OpType)
{
return false;
}
if (newNodeArgs != null)
{
newNodeArgs.Add(caseOpNode.Children[i]);
}
break;
}
// If the current then clause is a SoftCast then we do not attempt to simplify
// the case operation, since this may change the result type.
// Again, this really belongs in the CTreeGenerator as per SQL PT Work Item #300003327.
if (OpType.SoftCast
== caseOpNode.Children[i + 1].Op.OpType)
{
return false;
}
// Check to see if the when clause is a ConstantPredicate
if (caseOpNode.Children[i].Op.OpType
!= OpType.ConstantPredicate)
{
if (newNodeArgs != null)
{
newNodeArgs.Add(caseOpNode.Children[i]);
newNodeArgs.Add(caseOpNode.Children[i + 1]);
}
i += 2;
continue;
}
// Found a when-clause which is a constant predicate
var constPred = (ConstantPredicateOp)caseOpNode.Children[i].Op;
// Create the newArgs list, if we haven't done so already
if (newNodeArgs == null)
{
newNodeArgs = new List<Node>();
for (var j = 0; j < i; j++)
{
newNodeArgs.Add(caseOpNode.Children[j]);
}
}
// If the when-clause is the "true" predicate, then we simply ignore all
// the succeeding arguments. We make the "then" clause of this when-clause
// as the "else-clause" of the resulting caseOp
if (constPred.IsTrue)
{
newNodeArgs.Add(caseOpNode.Children[i + 1]);
break;
}
else
{
// Otherwise, we simply skip the when-then pair
PlanCompiler.Assert(constPred.IsFalse, "constant predicate must be either true or false");
i += 2;
continue;
}
}
// Did we see any changes? Simply return
if (newNodeArgs == null)
{
return false;
}
// Otherwise, we did do some processing
PlanCompiler.Assert(newNodeArgs.Count > 0, "new args list must not be empty");
// Is there only one expression in the args list - simply return that expression
if (newNodeArgs.Count == 1)
{
newNode = newNodeArgs[0];
}
else
{
newNode = context.Command.CreateNode(caseOp, newNodeArgs);
}
return true;
}
private static bool ProcessSimplifyCase_EliminateWhenClauses(
RuleProcessingContext context, CaseOp caseOp, Node caseOpNode, out Node newNode)
{
List <Node> newNodeArgs = null;
newNode = caseOpNode;
for (var i = 0; i < caseOpNode.Children.Count;)
{
// Special handling for the else clause
if (i == caseOpNode.Children.Count - 1)
{
// If the else clause is a SoftCast then we do not attempt to simplify
// the case operation, since this may change the result type.
// This really belongs in more general SoftCastOp logic in the CTreeGenerator
// that converts SoftCasts that could affect the result type of the query into
// a real cast or a trivial case statement, to preserve the result type.
// This is tracked by SQL PT Work Item #300003327.
if (OpType.SoftCast
== caseOpNode.Children[i].Op.OpType)
{
return(false);
}
if (newNodeArgs != null)
{
newNodeArgs.Add(caseOpNode.Children[i]);
}
break;
}
// If the current then clause is a SoftCast then we do not attempt to simplify
// the case operation, since this may change the result type.
// Again, this really belongs in the CTreeGenerator as per SQL PT Work Item #300003327.
if (OpType.SoftCast
== caseOpNode.Children[i + 1].Op.OpType)
{
return(false);
}
// Check to see if the when clause is a ConstantPredicate
if (caseOpNode.Children[i].Op.OpType
!= OpType.ConstantPredicate)
{
if (newNodeArgs != null)
{
newNodeArgs.Add(caseOpNode.Children[i]);
newNodeArgs.Add(caseOpNode.Children[i + 1]);
}
i += 2;
continue;
}
// Found a when-clause which is a constant predicate
var constPred = (ConstantPredicateOp)caseOpNode.Children[i].Op;
// Create the newArgs list, if we haven't done so already
if (newNodeArgs == null)
{
newNodeArgs = new List <Node>();
for (var j = 0; j < i; j++)
{
newNodeArgs.Add(caseOpNode.Children[j]);
}
}
// If the when-clause is the "true" predicate, then we simply ignore all
// the succeeding arguments. We make the "then" clause of this when-clause
// as the "else-clause" of the resulting caseOp
if (constPred.IsTrue)
{
newNodeArgs.Add(caseOpNode.Children[i + 1]);
break;
}
else
{
// Otherwise, we simply skip the when-then pair
PlanCompiler.Assert(constPred.IsFalse, "constant predicate must be either true or false");
i += 2;
continue;
}
}
// Did we see any changes? Simply return
if (newNodeArgs == null)
{
return(false);
}
// Otherwise, we did do some processing
PlanCompiler.Assert(newNodeArgs.Count > 0, "new args list must not be empty");
// Is there only one expression in the args list - simply return that expression
if (newNodeArgs.Count == 1)
{
newNode = newNodeArgs[0];
}
else
{
newNode = context.Command.CreateNode(caseOp, newNodeArgs);
}
return(true);
}
/// <summary>
/// Flattens a CaseOp - Specifically, if the CaseOp returns a structuredtype,
/// then the CaseOp is broken up so that we build up a "flat" record constructor
/// for that structured type, with each argument to the record constructor being
/// a (scalar) CaseOp. For example:
///
/// Case when b1 then e1 else e2 end
///
/// gets translated into:
///
/// RecordOp(case when b1 then e1.a else e2.a end,
/// case when b1 then e1.b else e2.b end,
/// ...)
///
/// The property extraction is optimized by producing only those properties
/// that have actually been requested.
/// </summary>
/// <param name="op">the CaseOp</param>
/// <param name="n">Node corresponding to the CaseOp</param>
/// <param name="typeInfo">Information about the type</param>
/// <param name="desiredProperties">Set of properties desired</param>
/// <returns></returns>
private Node FlattenCaseOp(CaseOp op, Node n, TypeInfo typeInfo, PropertyRefList desiredProperties)
{
// Build up a type constructor - with only as many fields filled in
// as are desired.
List<md.EdmProperty> fieldTypes = new List<md.EdmProperty>();
List<Node> fieldValues = new List<Node>();
foreach (PropertyRef pref in typeInfo.PropertyRefList)
{
// Is this property desired later?
if (!desiredProperties.Contains(pref))
{
continue;
}
md.EdmProperty property = typeInfo.GetNewProperty(pref);
// Build up an accessor for this property across each when/then clause
List<Node> caseChildren = new List<Node>();
for (int i = 0; i < n.Children.Count - 1; )
{
Node whenNode = Copy(n.Children[i]);
caseChildren.Add(whenNode);
i++;
Node propNode = BuildAccessorWithNulls(n.Children[i], property);
caseChildren.Add(propNode);
i++;
}
Node elseNode = BuildAccessorWithNulls(n.Children[n.Children.Count - 1], property);
caseChildren.Add(elseNode);
Node caseNode = m_command.CreateNode(m_command.CreateCaseOp(md.Helper.GetModelTypeUsage(property)), caseChildren);
fieldTypes.Add(property);
fieldValues.Add(caseNode);
}
NewRecordOp newRec = m_command.CreateNewRecordOp(typeInfo.FlattenedTypeUsage, fieldTypes);
return m_command.CreateNode(newRec, fieldValues);
}
/// <summary>
/// Default processing.
/// In addition, if the case statement is of the shape
/// case when X then NULL else Y, or
/// case when X then Y else NULL,
/// where Y is of row type and the types of the input CaseOp, the NULL and Y are the same,
/// marks that type as needing a null sentinel.
/// This allows in NominalTypeElimination the case op to be pushed inside Y's null sentinel.
/// </summary>
/// <param name="op"></param>
/// <param name="n"></param>
/// <returns></returns>
public override Node Visit(CaseOp op, Node n)
{
VisitScalarOpDefault(op, n);
//special handling to enable optimization
bool thenClauseIsNull;
if (PlanCompilerUtil.IsRowTypeCaseOpWithNullability(op, n, out thenClauseIsNull))
{
//Add a null sentinel for the row type
m_typesNeedingNullSentinel.Add(op.Type.EdmType.Identity);
}
return n;
}
public override void Visit(CaseOp op, Node n)
{
VisitScalarOpDefault(op, n);
Assert(
(n.Children.Count >= 3 && n.Children.Count % 2 == 1),
"CaseOp: Expected odd number of arguments, and at least 3; found {0}", n.Children.Count);
// Validate that each when statement is of type Boolean
for (var i = 0; i < n.Children.Count - 1; i += 2)
{
Assert(TypeSemantics.IsBooleanType(n.Children[i].Op.Type), "Encountered a when node with a non-boolean return type");
}
// Ensure that the then clauses, the else clause and the result type are all the same
for (var i = 1; i < n.Children.Count - 1; i += 2)
{
AssertEqualTypes(n.Op.Type, n.Children[i].Op.Type);
}
AssertEqualTypes(n.Op.Type, n.Children[n.Children.Count - 1].Op.Type);
}
/// <summary>
/// Copies a CaseOp
/// </summary>
/// <param name="op">The Op to Copy</param>
/// <param name="n">The Node that references the Op</param>
/// <returns>A copy of the original Node that references a copy of the original Op</returns>
public override Node Visit(CaseOp op, Node n)
{
return(CopyDefault(m_destCmd.CreateCaseOp(op.Type), n));
}
/// <summary>
/// Visitor pattern method for CaseOp
/// </summary>
/// <param name="op"> The CaseOp being visited </param>
/// <param name="n"> The Node that references the Op </param>
public virtual void Visit(CaseOp op, Node n)
{
VisitScalarOpDefault(op, n);
}
private static bool ProcessSimplifyCase_EliminateWhenClauses(
RuleProcessingContext context,
CaseOp caseOp,
System.Data.Entity.Core.Query.InternalTrees.Node caseOpNode,
out System.Data.Entity.Core.Query.InternalTrees.Node newNode)
{
List <System.Data.Entity.Core.Query.InternalTrees.Node> args = (List <System.Data.Entity.Core.Query.InternalTrees.Node>)null;
newNode = caseOpNode;
int index1 = 0;
while (index1 < caseOpNode.Children.Count)
{
if (index1 == caseOpNode.Children.Count - 1)
{
if (OpType.SoftCast == caseOpNode.Children[index1].Op.OpType)
{
return(false);
}
if (args != null)
{
args.Add(caseOpNode.Children[index1]);
break;
}
break;
}
if (OpType.SoftCast == caseOpNode.Children[index1 + 1].Op.OpType)
{
return(false);
}
if (caseOpNode.Children[index1].Op.OpType != OpType.ConstantPredicate)
{
if (args != null)
{
args.Add(caseOpNode.Children[index1]);
args.Add(caseOpNode.Children[index1 + 1]);
}
index1 += 2;
}
else
{
ConstantPredicateOp op = (ConstantPredicateOp)caseOpNode.Children[index1].Op;
if (args == null)
{
args = new List <System.Data.Entity.Core.Query.InternalTrees.Node>();
for (int index2 = 0; index2 < index1; ++index2)
{
args.Add(caseOpNode.Children[index2]);
}
}
if (op.IsTrue)
{
args.Add(caseOpNode.Children[index1 + 1]);
break;
}
System.Data.Entity.Core.Query.PlanCompiler.PlanCompiler.Assert(op.IsFalse, "constant predicate must be either true or false");
index1 += 2;
}
}
if (args == null)
{
return(false);
}
System.Data.Entity.Core.Query.PlanCompiler.PlanCompiler.Assert(args.Count > 0, "new args list must not be empty");
newNode = args.Count != 1 ? context.Command.CreateNode((Op)caseOp, args) : args[0];
return(true);
}
/// <summary>
/// CaseOp handling
///
/// Pushes its desired properties to each of the WHEN/ELSE clauses
/// </summary>
/// <param name="op"> </param>
/// <param name="n"> </param>
public override void Visit(CaseOp op, Node n)
{
// First find the properties that my parent expects from me
var pdProps = GetPropertyRefList(n);
// push down the same properties to my then/else clauses.
// the "when" clauses are irrelevant
for (var i = 1; i < n.Children.Count - 1; i += 2)
{
var cdProps = pdProps.Clone();
AddPropertyRefs(n.Children[i], cdProps);
}
AddPropertyRefs(n.Children[n.Children.Count - 1], pdProps.Clone());
// Now visit the children
VisitChildren(n);
}
// <summary>
// Copies a CaseOp
// </summary>
// <param name="op"> The Op to Copy </param>
// <param name="n"> The Node that references the Op </param>
// <returns> A copy of the original Node that references a copy of the original Op </returns>
public override Node Visit(CaseOp op, Node n)
{
return CopyDefault(m_destCmd.CreateCaseOp(op.Type), n);
}
/// <summary>
/// We don't yet support nest pullups over Case
/// </summary>
/// <param name="op"></param>
/// <param name="n"></param>
/// <returns></returns>
public override Node Visit(CaseOp op, Node n)
{
// Make sure we don't have a child that is a nest op.
foreach (Node chi in n.Children)
{
if (chi.Op.OpType == OpType.Collect)
{
throw EntityUtil.NestingNotSupported(op, chi.Op);
}
else if (chi.Op.OpType == OpType.VarRef)
{
Var refVar = ((VarRefOp)chi.Op).Var;
if (m_definingNodeMap.ContainsKey(refVar))
{
throw EntityUtil.NestingNotSupported(op, chi.Op);
}
}
}
return VisitDefault(n);
}
