mcs/class/System.Core/System.Linq.Parallel/QueryCheckerVisitor.cs

   1 //
   2 // QueryCheckerVisitor.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2010 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0 || MOBILE
  28 using System;
  29 using System.Threading;
  30 using System.Linq.Parallel.QueryNodes;
  31
  32 namespace System.Linq.Parallel
  33 {
  34         using OptionsList = Tuple<ParallelMergeOptions?, ParallelExecutionMode?, CancellationToken?, int, CancellationTokenSource>;
  35
  36         internal class QueryCheckerVisitor : INodeVisitor
  37         {
  38                 const int minSequentialThreshold = 20;
  39
  40                 // Information gathering
  41                 ParallelMergeOptions? options = null;
  42                 ParallelExecutionMode? mode = null;
  43                 CancellationToken? token = null;
  44                 int? degreeOfParallelism = null;
  45                 CancellationToken implementerToken = CancellationToken.None;
  46
  47                 int partitionCount;
  48                 bool? behindOrderGuard = null;
  49
  50                 internal QueryCheckerVisitor (int partitionCount)
  51                 {
  52                         this.partitionCount = partitionCount;
  53                 }
  54
  55                 #region INodeVisitor implementation
  56                 public void Visit (QueryBaseNode node)
  57                 {
  58                         // Nothing to do atm. Later we can check if the node is a
  59                         // Take or a Skip and set accordingly UseStrip
  60                 }
  61
  62                 public void Visit (QueryChildNode node)
  63                 {
  64                         node.Parent.Visit (this);
  65                 }
  66
  67                 public void Visit (QueryOptionNode node)
  68                 {
  69                         MergeOptions (node.GetOptions ());
  70
  71                         Visit ((QueryChildNode)node);
  72                 }
  73
  74                 public void Visit (QueryStartNode node)
  75                 {
  76                         if (behindOrderGuard == null)
  77                                 behindOrderGuard = false;
  78                         if (degreeOfParallelism != null)
  79                                 partitionCount = degreeOfParallelism.Value;
  80
  81                         int count;
  82                         if ((count = node.Count) != -1 && count < minSequentialThreshold)
  83                                 ShouldBeSequential = true;
  84                 }
  85
  86                 public void Visit (QueryStreamNode node)
  87                 {
  88                         if (node.IsIndexed)
  89                                 UseStrip = true;
  90
  91                         Visit ((QueryChildNode)node);
  92                 }
  93
  94                 public void Visit (QueryOrderGuardNode node)
  95                 {
  96                         if (behindOrderGuard == null) {
  97                                 if (node.EnsureOrder) {
  98                                         behindOrderGuard = true;
  99                                         //UseStrip = true;
 100                                 } else {
 101                                         behindOrderGuard = false;
 102                                 }
 103                         }
 104
 105                         Visit ((QueryStreamNode)node);
 106                 }
 107
 108                 public void Visit (QueryMuxNode node)
 109                 {
 110                         Visit ((QueryChildNode)node);
 111                 }
 112
 113                 public void Visit (QueryHeadWorkerNode node)
 114                 {
 115                         // Wouldn't it be better with standard Linq?
 116                         if (node.Count.HasValue && node.Count < partitionCount)
 117                                 ShouldBeSequential = true;
 118
 119                         Visit ((QueryStreamNode)node);
 120                 }
 121                 #endregion
 122
 123                 internal QueryOptions Options {
 124                         get {
 125                                 return new QueryOptions (options, mode, token == null ? CancellationToken.None : token.Value,
 126                                                          UseStrip, behindOrderGuard, partitionCount, implementerToken, ShouldBeSequential);
 127                         }
 128                 }
 129
 130                 internal bool UseStrip {
 131                         get;
 132                         private set;
 133                 }
 134
 135                 internal bool BehindOrderGuard {
 136                         get {
 137                                 return behindOrderGuard.Value;
 138                         }
 139                 }
 140
 141                 internal bool ShouldBeSequential {
 142                         get;
 143                         private set;
 144                 }
 145
 146                 void MergeOptions (OptionsList list)
 147                 {
 148                         if (list.Item1 != null) {
 149                                 if (options == null)
 150                                         options = list.Item1;
 151                                 else
 152                                         Throw ("WithMergeOptions");
 153                         }
 154
 155                         if (list.Item2 != null) {
 156                                 if (mode == null)
 157                                         mode = list.Item2;
 158                                 else
 159                                         Throw ("WithExecutionMode");
 160                         }
 161
 162                         if (list.Item3 != null) {
 163                                 if (token == null)
 164                                         token = list.Item3;
 165                                 else
 166                                         Throw ("WithCancellationToken");
 167                         }
 168
 169                         if (list.Item4 != -1) {
 170                                 if (degreeOfParallelism == null)
 171                                         degreeOfParallelism = list.Item4;
 172                                 else
 173                                         Throw ("WithDegreeOfParallelism");
 174                         }
 175
 176                         // That one is treated specially
 177                         if (list.Item5 != null) {
 178                                 implementerToken = implementerToken.Chain (list.Item5);
 179                         }
 180                 }
 181
 182                 void Throw (string methName)
 183                 {
 184                         throw new InvalidOperationException ("You can't have more than one " + methName + " node in a query");
 185                 }
 186         }
 187 }
 188 #endif