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//
// QueryCheckerVisitor.cs
//
// Author:
// Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
//
// Copyright (c) 2010 Jérémie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#if NET_4_0
using System;
using System.Threading;
using System.Linq.Parallel.QueryNodes;
namespace System.Linq.Parallel
{
using OptionsList = Tuple<ParallelMergeOptions?, ParallelExecutionMode?, CancellationToken?, int, CancellationTokenSource>;
internal class QueryCheckerVisitor : INodeVisitor
{
const int minSequentialThreshold = 20;
// Information gathering
ParallelMergeOptions? options = null;
ParallelExecutionMode? mode = null;
CancellationToken? token = null;
int? degreeOfParallelism = null;
CancellationToken implementerToken = CancellationToken.None;
int partitionCount;
bool? behindOrderGuard = null;
internal QueryCheckerVisitor (int partitionCount)
{
this.partitionCount = partitionCount;
}
#region INodeVisitor implementation
public void Visit (QueryBaseNode node)
{
// Nothing to do atm. Later we can check if the node is a
// Take or a Skip and set accordingly UseStrip
}
public void Visit (QueryChildNode node)
{
node.Parent.Visit (this);
}
public void Visit (QueryOptionNode node)
{
MergeOptions (node.GetOptions ());
Visit ((QueryChildNode)node);
}
public void Visit (QueryStartNode node)
{
if (behindOrderGuard == null)
behindOrderGuard = false;
if (degreeOfParallelism != null)
partitionCount = degreeOfParallelism.Value;
int count;
if ((count = node.Count) != -1 && count < minSequentialThreshold)
ShouldBeSequential = true;
}
public void Visit (QueryStreamNode node)
{
if (node.IsIndexed)
UseStrip = true;
Visit ((QueryChildNode)node);
}
public void Visit (QueryOrderGuardNode node)
{
if (behindOrderGuard == null) {
if (node.EnsureOrder) {
behindOrderGuard = true;
//UseStrip = true;
} else {
behindOrderGuard = false;
}
}
Visit ((QueryStreamNode)node);
}
public void Visit (QueryMuxNode node)
{
Visit ((QueryChildNode)node);
}
public void Visit (QueryHeadWorkerNode node)
{
// Wouldn't it be better with standard Linq?
if (node.Count.HasValue && node.Count < partitionCount)
ShouldBeSequential = true;
Visit ((QueryStreamNode)node);
}
#endregion
internal QueryOptions Options {
get {
return new QueryOptions (options, mode, token == null ? CancellationToken.None : token.Value,
UseStrip, behindOrderGuard, partitionCount, implementerToken, ShouldBeSequential);
}
}
internal bool UseStrip {
get;
private set;
}
internal bool BehindOrderGuard {
get {
return behindOrderGuard.Value;
}
}
internal bool ShouldBeSequential {
get;
private set;
}
void MergeOptions (OptionsList list)
{
if (list.Item1 != null) {
if (options == null)
options = list.Item1;
else
Throw ("WithMergeOptions");
}
if (list.Item2 != null) {
if (mode == null)
mode = list.Item2;
else
Throw ("WithExecutionMode");
}
if (list.Item3 != null) {
if (token == null)
token = list.Item3;
else
Throw ("WithCancellationToken");
}
if (list.Item4 != -1) {
if (degreeOfParallelism == null)
degreeOfParallelism = list.Item4;
else
Throw ("WithDegreeOfParallelism");
}
// That one is treated specially
if (list.Item5 != null) {
implementerToken = implementerToken.Chain (list.Item5);
}
}
void Throw (string methName)
{
throw new InvalidOperationException ("You can't have more than one " + methName + " node in a query");
}
}
}
#endif
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