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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Query / PlanCompiler / JoinElimination.cs / 1305376 / JoinElimination.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.Globalization; using System.Data.Query.InternalTrees; namespace System.Data.Query.PlanCompiler { ////// The JoinElimination module is intended to do just that - eliminate unnecessary joins. /// This module deals with the following kinds of joins /// * Self-joins: The join can be eliminated, and either of the table instances can be /// used instead /// * Implied self-joins: Same as above /// * PK-FK joins: (More generally, UK-FK joins): Eliminate the join, and use just the FK table, if no /// column of the PK table is used (other than the join condition) /// * PK-PK joins: Eliminate the right side table, if we have a left-outer join /// internal class JoinElimination : BasicOpVisitorOfNode { #region private state private PlanCompiler m_compilerState; private Command Command { get { return m_compilerState.Command; } } private ConstraintManager ConstraintManager { get { return m_compilerState.ConstraintManager; } } private Dictionarym_joinGraphUnnecessaryMap = new Dictionary (); private VarRemapper m_varRemapper; private bool m_treeModified = false; private VarRefManager m_varRefManager; #endregion #region constructors private JoinElimination(PlanCompiler compilerState) { m_compilerState = compilerState; m_varRemapper = new VarRemapper(m_compilerState.Command); m_varRefManager = new VarRefManager(m_compilerState.Command); } #endregion #region public surface internal static bool Process(PlanCompiler compilerState) { JoinElimination je = new JoinElimination(compilerState); je.Process(); return je.m_treeModified; } #endregion #region private methods /// /// Invokes the visitor /// private void Process() { this.Command.Root = VisitNode(this.Command.Root); } #region JoinHelpers #region Building JoinGraphs ////// Do we need to build a join graph for this node - returns false, if we've already /// processed this /// /// ///private bool NeedsJoinGraph(Node joinNode) { return !m_joinGraphUnnecessaryMap.ContainsKey(joinNode); } /// /// Do the real processing of the join graph. /// /// current join node ///modified join node private Node ProcessJoinGraph(Node joinNode) { // Build the join graph JoinGraph joinGraph = new JoinGraph(this.Command, this.ConstraintManager, this.m_varRefManager, joinNode); // Get the transformed node tree VarMap remappedVars; DictionaryprocessedNodes; Node newNode = joinGraph.DoJoinElimination(out remappedVars, out processedNodes); // Get the set of vars that need to be renamed foreach (KeyValuePair kv in remappedVars) { m_varRemapper.AddMapping(kv.Key, kv.Value); } // get the set of nodes that have already been processed foreach (Node n in processedNodes.Keys) { m_joinGraphUnnecessaryMap[n] = n; } return newNode; } /// /// Default handler for a node. Simply visits the children, then handles any var /// remapping, and then recomputes the node info /// /// ///private Node VisitDefaultForAllNodes(Node n) { VisitChildren(n); m_varRemapper.RemapNode(n); this.Command.RecomputeNodeInfo(n); return n; } #endregion #endregion #region Visitor overrides /// /// Invokes default handling for a node and adds the child-parent tracking info to the VarRefManager. /// /// ///protected override Node VisitDefault(Node n) { m_varRefManager.AddChildren(n); return VisitDefaultForAllNodes(n); } #region RelOps #region JoinOps /// /// Build a join graph for this node for this node if necessary, and process it /// /// current join op /// current join node ///protected override Node VisitJoinOp(JoinBaseOp op, Node joinNode) { Node newNode; // Build and process a join graph if necessary if (NeedsJoinGraph(joinNode)) { newNode = ProcessJoinGraph(joinNode); if (newNode != joinNode) { m_treeModified = true; } } else { newNode = joinNode; } // Now do the default processing (ie) visit the children, compute the nodeinfo etc. return VisitDefaultForAllNodes(newNode); } #endregion #endregion #endregion #endregion } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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