VarRemapper.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 / VarRemapper.cs / 1305376 / VarRemapper.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner  [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System; 
using System.Collections.Generic;
//using System.Diagnostics; // Please use PlanCompiler.Assert instead of Debug.Assert in this class...
using System.Data.Query.InternalTrees;
 
namespace System.Data.Query.PlanCompiler
{ 
    ///  
    /// The VarRemapper is a utility class that can be used to "remap" Var references
    /// in a node, or a subtree. 
    /// 
    internal class VarRemapper : BasicOpVisitor
    {
        #region Private state 
        private readonly Dictionary m_varMap;
        protected readonly Command m_command; 
        #endregion 

        #region Constructors 
        /// 
        /// Internal constructor
        /// 
        /// Current iqt command 
        internal VarRemapper(Command command)
            :this(command, new Dictionary()) 
        { 
        }
 
        /// 
        /// Internal constructor
        /// 
        /// Current iqt command 
        /// Var map to be used
        internal VarRemapper(Command command, Dictionary varMap) 
        { 
            m_command = command;
            m_varMap = varMap; 
        }
        #endregion

        #region Public surface 
        /// 
        /// Add a mapping for "oldVar" - when the replace methods are invoked, they 
        /// will replace all references to "oldVar" by "newVar" 
        /// 
        /// var to replace 
        /// the replacement var
        internal void AddMapping(Var oldVar, Var newVar)
        {
            m_varMap[oldVar] = newVar; 
        }
 
        ///  
        /// Update vars in just this node (and not the entire subtree)
        /// Does *not* recompute the nodeinfo - there are at least some consumers of this 
        /// function that do not want the recomputation - transformation rules, for example
        /// 
        /// current node
        internal virtual void RemapNode(Node node) 
        {
            if (m_varMap.Count == 0) 
            { 
                return;
            } 
            VisitNode(node);
        }

        ///  
        /// Update vars in this subtree. Recompute the nodeinfo along the way
        ///  
        /// subtree to "remap" 
        internal virtual void RemapSubtree(Node subTree)
        { 
            if (m_varMap.Count == 0)
            {
                return;
            } 

            foreach (Node chi in subTree.Children) 
            { 
                RemapSubtree(chi);
            } 

            RemapNode(subTree);
            m_command.RecomputeNodeInfo(subTree);
        } 

        ///  
        /// Produce a a new remapped varList 
        /// 
        ///  
        /// remapped varList
        internal VarList RemapVarList(VarList varList)
        {
            return Command.CreateVarList(MapVars(varList)); 
        }
 
        ///  
        /// Remap the given varList using the given varMap
        ///  
        /// 
        /// 
        /// 
        internal static VarList RemapVarList(Command command, Dictionary varMap, VarList varList) 
        {
            VarRemapper varRemapper = new VarRemapper(command, varMap); 
            return varRemapper.RemapVarList(varList); 
        }
        #endregion 

        #region Private methods
        /// 
        /// Get the mapping for a Var - returns the var itself, mapping was found 
        /// 
        ///  
        ///  
        private Var Map(Var v)
        { 
            Var newVar;
            while (true)
            {
                if (!m_varMap.TryGetValue(v, out newVar)) 
                {
                    return v; 
                } 
                v = newVar;
            } 
        }

        private IEnumerable MapVars(IEnumerable vars)
        { 
            foreach (Var v in vars)
            { 
                yield return Map(v); 
            }
        } 

        private void Map(VarVec vec)
        {
            VarVec newVec = m_command.CreateVarVec(MapVars(vec)); 
            vec.InitFrom(newVec);
        } 
 
        private void Map(VarList varList)
        { 
            VarList newList = Command.CreateVarList(MapVars(varList));
            varList.Clear();
            varList.AddRange(newList);
        } 

        private void Map(VarMap varMap) 
        { 
            VarMap newVarMap = new VarMap();
            foreach (KeyValuePair kv in varMap) 
            {
                Var newVar = Map(kv.Value);
                newVarMap.Add(kv.Key, newVar);
            } 
            varMap.Clear();
            foreach (KeyValuePair kv in newVarMap) 
            { 
                varMap.Add(kv.Key, kv.Value);
            } 
        }
        private void Map(List sortKeys)
        {
            VarVec sortVars = m_command.CreateVarVec(); 
            bool hasDuplicates = false;
 
            // 
            // Map each var in the sort list. Remapping may introduce duplicates, and
            // we should get rid of duplicates, since sql doesn't like them 
            //
            foreach (InternalTrees.SortKey sk in sortKeys)
            {
                sk.Var = Map(sk.Var); 
                if (sortVars.IsSet(sk.Var))
                { 
                    hasDuplicates = true; 
                }
                sortVars.Set(sk.Var); 
            }

            //
            // Get rid of any duplicates 
            //
            if (hasDuplicates) 
            { 
                List newSortKeys = new List(sortKeys);
                sortKeys.Clear(); 
                sortVars.Clear();
                foreach (InternalTrees.SortKey sk in newSortKeys)
                {
                    if (!sortVars.IsSet(sk.Var)) 
                    {
                        sortKeys.Add(sk); 
                    } 
                    sortVars.Set(sk.Var);
                } 
            }
        }

        #region VisitorMethods 
        /// 
        ///  Default visitor for a node - does not visit the children 
        /// The reason we have this method is because the default VisitDefault 
        /// actually visits the children, and we don't want to do that
        ///  
        /// 
        protected override void VisitDefault(Node n)
        {
            // Do nothing. 
        }
 
        #region ScalarOps 
        public override void Visit(VarRefOp op, Node n)
        { 
            VisitScalarOpDefault(op, n);
            Var newVar = Map(op.Var);
            if (newVar != op.Var)
            { 
                n.Op = m_command.CreateVarRefOp(newVar);
            } 
        } 
        #endregion
 
        #region AncillaryOps
        #endregion

        #region PhysicalOps 
        protected override void VisitNestOp(NestBaseOp op, Node n)
        { 
            throw EntityUtil.NotSupported(); 
        }
 
        public override void Visit(PhysicalProjectOp op, Node n)
        {
            VisitPhysicalOpDefault(op, n);
            Map(op.Outputs); 

            SimpleCollectionColumnMap newColumnMap = (SimpleCollectionColumnMap)ColumnMapTranslator.Translate(op.ColumnMap, m_varMap); 
            n.Op = m_command.CreatePhysicalProjectOp(op.Outputs, newColumnMap); 
        }
        #endregion 

        #region RelOps
        protected override void VisitGroupByOp(GroupByBaseOp op, Node n)
        { 
            VisitRelOpDefault(op, n);
            Map(op.Outputs); 
            Map(op.Keys); 
        }
        public override void Visit(GroupByIntoOp op, Node n) 
        {
            VisitGroupByOp(op, n);
            Map(op.Inputs);
        } 
        public override void Visit(DistinctOp op, Node n)
        { 
            VisitRelOpDefault(op, n); 
            Map(op.Keys);
        } 
        public override void Visit(ProjectOp op, Node n)
        {
            VisitRelOpDefault(op, n);
            Map(op.Outputs); 
        }
        public override void Visit(UnnestOp op, Node n) 
        { 
            VisitRelOpDefault(op, n);
            Var newVar = Map(op.Var); 
            if (newVar != op.Var)
            {
                n.Op = m_command.CreateUnnestOp(newVar, op.Table);
            } 
        }
        protected override void VisitSetOp(SetOp op, Node n) 
        { 
            VisitRelOpDefault(op, n);
            Map(op.VarMap[0]); 
            Map(op.VarMap[1]);
        }
        protected override void VisitSortOp(SortBaseOp op, Node n)
        { 
            VisitRelOpDefault(op, n);
            Map(op.Keys); 
        } 
        #endregion
 
        #endregion

        #endregion
    } 
}

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