VarRefManager.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Query / PlanCompiler / VarRefManager.cs / 1305376 / VarRefManager.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner  [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System; 
using System.Collections.Generic;
using System.Globalization;
using System.Diagnostics;
using System.Data.Query.InternalTrees; 

namespace System.Data.Query.PlanCompiler 
{ 
    /// 
    /// This is a halper module for  
    /// The VarRefManager keeps track of the child-parent relationships in order to be able
    /// to decide whether a given var is referenced by children on right-side relatives of a given node.
    /// It is used in JoinElimination when deciding whether it is possible to eliminate the child table participating
    /// in a left-outer join when there is a 1 - 0..1 FK relationship. 
    /// 
    internal class VarRefManager 
    { 
        #region Internal State
        private Dictionary m_nodeToParentMap;   //child-parent mapping 
        private Dictionary m_nodeToSiblingNumber;   //the index of the given node among its siblings, i.e. 0 for a first child
        Command m_command;
        #endregion
 
        #region Constructor
        ///  
        /// Constructs a new VarRefManager given a command. 
        /// 
        ///  
        internal VarRefManager(Command command)
        {
            m_nodeToParentMap = new Dictionary();
            m_nodeToSiblingNumber = new Dictionary(); 
            m_command = command;
        } 
        #endregion 

        #region Public Methods 

        /// 
        /// Tracks the information that the given node is a parent of its children (one level only)
        ///  
        /// 
        internal void AddChildren(Node parent) 
        { 
            for(int i=0; i< parent.Children.Count; i++)
            { 
                //We do not use add on purpose, we may be updating a child's parent after join elimination in a subtree
                m_nodeToParentMap[parent.Children[i]] = parent;
                m_nodeToSiblingNumber[parent.Children[i]] = i;
            } 
        }
 
        ///  
        /// Determines whether any var from a given list of keys is referenced by any of defining node's right relatives,
        /// with the exception of the relatives brunching at the given targetJoinNode. 
        /// 
        /// A list of vars to check for
        /// The node considered to be the defining node
        /// The relatives branching at this node are skipped 
        /// False, only it can determine that not a single var from a given list of keys is referenced by any
        /// of defining node's right relatives, with the exception of the relatives brunching at the given targetJoinNode.  
        internal bool HasKeyReferences(VarVec keys, Node definingNode, Node targetJoinNode) 
        {
            Node currentChild = definingNode; 
            Node parent;
            bool continueUp = true;

            while (continueUp & m_nodeToParentMap.TryGetValue(currentChild, out parent)) 
            {
                if (parent != targetJoinNode) 
                { 
                    // Check the parent
                    if (HasVarReferencesShallow(parent, keys, m_nodeToSiblingNumber[currentChild], out continueUp)) 
                    {
                        return true;
                    }
 
                    //Check all the siblings to the right
                    for (int i = m_nodeToSiblingNumber[currentChild] + 1; i < parent.Children.Count; i++) 
                    { 
                        if (parent.Children[i].GetNodeInfo(m_command).ExternalReferences.Overlaps(keys))
                        { 
                            return true;
                        }
                    }
                } 
                currentChild = parent;
            } 
            return false; 
        }
 
        #endregion

        #region Private Methods
        ///  
        /// Checks whether the given node has references to any of the vars in the given VarVec.
        /// It only checks the given node, not its children. 
        ///  
        /// The node to check
        /// The list of vars to check for 
        /// The index of the node's subree from which this var is coming.
        /// This is used for SetOp-s, to be able to locate the appropriate var map that will give the
        /// vars corresponding to the given once
        /// If the OpType of the node's Op is such that it 'hides' the input, i.e. 
        /// the decision of whether the given vars are referenced can be made on this level, it returns true,
        /// false otherwise 
        /// True if the given node has references to any of the vars in the given VarVec, false otherwise 
        private static bool HasVarReferencesShallow(Node node, VarVec vars, int childIndex, out bool continueUp)
        { 
            switch (node.Op.OpType)
            {
                case OpType.ConstrainedSort:
                case OpType.Sort: 
                    continueUp = true;
                    return HasVarReferences(((SortBaseOp)node.Op).Keys, vars); 
 
                case OpType.Distinct:
                    continueUp = false; 
                    return HasVarReferences(((DistinctOp)node.Op).Keys, vars);

                case OpType.Except:
                case OpType.Intersect: 
                case OpType.UnionAll:
                    continueUp = false; 
                    return HasVarReferences((SetOp)node.Op, vars, childIndex); 

                case OpType.GroupBy: 
                    continueUp = false;
                    return HasVarReferences(((GroupByOp)node.Op).Keys, vars);

                case OpType.PhysicalProject: 
                    continueUp = false;
                    return HasVarReferences(((PhysicalProjectOp)node.Op).Outputs, vars); 
 
                case OpType.Project:
                    continueUp = false; 
                    return HasVarReferences(((ProjectOp)node.Op).Outputs, vars);

                default:
                    continueUp = true; 
                    return false;
            } 
        } 

        ///  
        /// Does the gvien VarList overlap with the given VarVec
        /// 
        /// 
        ///  
        /// 
        private static bool HasVarReferences(VarList listToCheck, VarVec vars) 
        { 
            foreach (Var var in vars)
            { 
                if (listToCheck.Contains(var))
                {
                    return true;
                } 
            }
            return false; 
        } 

        ///  
        /// Do the two given varVecs overlap
        /// 
        /// 
        ///  
        /// 
        private static bool HasVarReferences(VarVec listToCheck, VarVec vars) 
        { 
            return listToCheck.Overlaps(vars);
        } 

        /// 
        /// Does the given list of sort keys contain a key with a var that is the given VarVec
        ///  
        /// 
        ///  
        ///  
        private static bool HasVarReferences(List listToCheck, VarVec vars)
        { 
            foreach (InternalTrees.SortKey key in listToCheck)
            {
                if (vars.IsSet(key.Var))
                { 
                    return true;
                } 
            } 
            return false;
        } 

        /// 
        /// Does the list of outputs of the given SetOp contain a var
        /// from the given VarVec defined by the SetOp's child with the given index 
        /// 
        ///  
        ///  
        /// 
        ///  
        private static bool HasVarReferences(SetOp op, VarVec vars, int index)
        {
            foreach (Var var in op.VarMap[index].Values)
            { 
                if (vars.IsSet(var))
                { 
                    return true; 
                }
            } 
            return false;
        }
        #endregion
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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