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//---------------------------------------------------------------------
// <copyright file="CompiledELinqQueryState.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
namespace System.Data.Objects.ELinq
{
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data.Common.CommandTrees;
using System.Data.Common.QueryCache;
using System.Data.Metadata.Edm;
using System.Data.Objects;
using System.Data.Objects.Internal;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
/// <summary>
/// Models a compiled Linq to Entities ObjectQuery
/// </summary>
internal sealed class CompiledELinqQueryState : ELinqQueryState
{
private readonly Guid _cacheToken;
private readonly object[] _parameterValues;
private CompiledQueryCacheEntry _cacheEntry;
/// <summary>
/// Factory method to create a new compiled query state instance
/// </summary>
/// <param name="elementType">The element type of the new instance (the 'T' of the ObjectQuery<T> that the new state instance will back)"</param>
/// <param name="context">The object context with which the new instance should be associated</param>
/// <param name="lambda">The compiled query definition, as a <see cref="LambdaExpression"/></param>
/// <param name="cacheToken">The cache token to use when retrieving or storing the new instance's execution plan in the query cache</param>
/// <param name="parameterValues">The values passed into the CompiledQuery delegate</param>
internal CompiledELinqQueryState(Type elementType, ObjectContext context, LambdaExpression lambda, Guid cacheToken, object[] parameterValues)
: base(elementType, context, lambda)
{
EntityUtil.CheckArgumentNull(parameterValues, "parameterValues");
_cacheToken = cacheToken;
_parameterValues = parameterValues;
this.EnsureParameters();
this.Parameters.SetReadOnly(true);
}
internal override ObjectQueryExecutionPlan GetExecutionPlan(MergeOption? forMergeOption)
{
Debug.Assert(this.Span == null, "Include span specified on compiled LINQ-based ObjectQuery instead of within the expression tree?");
Debug.Assert(this._cachedPlan == null, "Cached plan should not be set on compiled LINQ queries");
// Metadata is required to generate the execution plan or to retrieve it from the cache.
this.ObjectContext.EnsureMetadata();
ObjectQueryExecutionPlan plan = null;
CompiledQueryCacheEntry cacheEntry = this._cacheEntry;
bool useCSharpNullComparisonBehavior = this.ObjectContext.ContextOptions.UseCSharpNullComparisonBehavior;
if (cacheEntry != null)
{
// The cache entry has already been retrieved, so compute the effective merge option with the following precedence:
// 1. The merge option specified as the argument to Execute(MergeOption), and so to this method
// 2. The merge option set using ObjectQuery.MergeOption
// 3. The propagated merge option as recorded in the cache entry
// 4. The global default merge option.
MergeOption mergeOption = EnsureMergeOption(forMergeOption, this.UserSpecifiedMergeOption, cacheEntry.PropagatedMergeOption);
// Ask for the corresponding execution plan
plan = cacheEntry.GetExecutionPlan(mergeOption, useCSharpNullComparisonBehavior);
if (plan == null)
{
// Convert the LINQ expression to produce a command tree
ExpressionConverter converter = this.CreateExpressionConverter();
DbExpression queryExpression = converter.Convert();
ReadOnlyCollection<KeyValuePair<ObjectParameter, QueryParameterExpression>> parameters = converter.GetParameters();
// Prepare the execution plan using the command tree and the computed effective merge option
DbQueryCommandTree tree = DbQueryCommandTree.FromValidExpression(this.ObjectContext.MetadataWorkspace, DataSpace.CSpace, queryExpression);
plan = ObjectQueryExecutionPlan.Prepare(this.ObjectContext, tree, this.ElementType, mergeOption, converter.PropagatedSpan, parameters, converter.AliasGenerator);
// Update and retrieve the execution plan
plan = cacheEntry.SetExecutionPlan(plan, useCSharpNullComparisonBehavior);
}
}
else
{
// This instance does not yet have a reference to a cache entry.
// First, attempt to retrieve an existing cache entry.
QueryCacheManager cacheManager = this.ObjectContext.MetadataWorkspace.GetQueryCacheManager();
CompiledQueryCacheKey cacheKey = new CompiledQueryCacheKey(this._cacheToken);
if (cacheManager.TryCacheLookup(cacheKey, out cacheEntry))
{
// An entry was found in the cache, so compute the effective merge option based on its propagated merge option,
// and use the UseCSharpNullComparisonBehavior flag to retrieve the corresponding execution plan.
this._cacheEntry = cacheEntry;
MergeOption mergeOption = EnsureMergeOption(forMergeOption, this.UserSpecifiedMergeOption, cacheEntry.PropagatedMergeOption);
plan = cacheEntry.GetExecutionPlan(mergeOption, useCSharpNullComparisonBehavior);
}
// If no cache entry was found or if the cache entry did not contain the required execution plan, the plan is still null at this point.
if (plan == null)
{
// The execution plan needs to be produced, so create an appropriate expression converter and generate the query command tree.
ExpressionConverter converter = this.CreateExpressionConverter();
DbExpression queryExpression = converter.Convert();
ReadOnlyCollection<KeyValuePair<ObjectParameter, QueryParameterExpression>> parameters = converter.GetParameters();
DbQueryCommandTree tree = DbQueryCommandTree.FromValidExpression(this.ObjectContext.MetadataWorkspace, DataSpace.CSpace, queryExpression);
// If a cache entry for this compiled query's cache key was not successfully retrieved, then it must be created now.
// Note that this is only possible after converting the LINQ expression and discovering the propagated merge option,
// which is required in order to create the cache entry.
if (cacheEntry == null)
{
// Create the cache entry using this instance's cache token and the propagated merge option (which may be null)
cacheEntry = new CompiledQueryCacheEntry(cacheKey, converter.PropagatedMergeOption);
// Attempt to add the entry to the cache. If an entry was added in the meantime, use that entry instead.
QueryCacheEntry foundEntry;
if (cacheManager.TryLookupAndAdd(cacheEntry, out foundEntry))
{
cacheEntry = (CompiledQueryCacheEntry)foundEntry;
}
// We now have a cache entry, so hold onto it for future use.
this._cacheEntry = cacheEntry;
}
// Recompute the effective merge option in case a cache entry was just constructed above
MergeOption mergeOption = EnsureMergeOption(forMergeOption, this.UserSpecifiedMergeOption, cacheEntry.PropagatedMergeOption);
// Ask the (retrieved or constructed) cache entry for the corresponding execution plan.
plan = cacheEntry.GetExecutionPlan(mergeOption, useCSharpNullComparisonBehavior);
if (plan == null)
{
// The plan is not present, so prepare it now using the computed effective merge option
plan = ObjectQueryExecutionPlan.Prepare(this.ObjectContext, tree, this.ElementType, mergeOption, converter.PropagatedSpan, parameters, converter.AliasGenerator);
// Update the execution plan on the cache entry.
// If the execution plan was set in the meantime, SetExecutionPlan will return that value, otherwise it will return 'plan'.
plan = cacheEntry.SetExecutionPlan(plan, useCSharpNullComparisonBehavior);
}
}
}
// Get parameters from the plan and set them.
ObjectParameterCollection currentParams = this.EnsureParameters();
if (plan.CompiledQueryParameters != null && plan.CompiledQueryParameters.Count > 0)
{
currentParams.SetReadOnly(false);
currentParams.Clear();
foreach (KeyValuePair<ObjectParameter, QueryParameterExpression> pair in plan.CompiledQueryParameters)
{
// Parameters retrieved from the CompiledQueryParameters collection must be cloned before being added to the query.
// The cached plan is shared and when used in multithreaded scenarios failing to clone the parameter would result
// in the code below updating the values of shared parameter instances saved in the cached plan and used by all
// queries using that plan, regardless of the values they were actually invoked with, causing incorrect results
// when those queries were later executed.
//
ObjectParameter convertedParam = pair.Key.ShallowCopy();
QueryParameterExpression parameterExpression = pair.Value;
currentParams.Add(convertedParam);
if (parameterExpression != null)
{
convertedParam.Value = parameterExpression.EvaluateParameter(_parameterValues);
}
}
}
currentParams.SetReadOnly(true);
Debug.Assert(plan != null, "Failed to produce an execution plan?");
return plan;
}
/// <summary>
/// Overrides GetResultType and attempts to first retrieve the result type from the cache entry.
/// </summary>
/// <returns>The query result type from this compiled query's cache entry, if possible; otherwise defers to <see cref="ELinqQueryState.GetResultType"/></returns>
protected override TypeUsage GetResultType()
{
CompiledQueryCacheEntry cacheEntry = this._cacheEntry;
TypeUsage resultType;
if (cacheEntry != null &&
cacheEntry.TryGetResultType(out resultType))
{
return resultType;
}
return base.GetResultType();
}
/// <summary>
/// Gets a LINQ expression that defines this query.
/// This is overridden to remove parameter references from the underlying expression,
/// producing an expression that contains the values of those parameters as <see cref="ConstantExpression"/>s.
/// </summary>
internal override Expression Expression
{
get
{
return CreateDonateableExpressionVisitor.Replace((LambdaExpression)base.Expression, ObjectContext, _parameterValues);
}
}
/// <summary>
/// Overrides CreateExpressionConverter to return a converter that uses a binding context based on the compiled query parameters,
/// rather than a default binding context.
/// </summary>
/// <returns>An expression converter appropriate for converting this compiled query state instance</returns>
protected override ExpressionConverter CreateExpressionConverter()
{
LambdaExpression lambda = (LambdaExpression)base.Expression;
Funcletizer funcletizer = Funcletizer.CreateCompiledQueryEvaluationFuncletizer(this.ObjectContext, lambda.Parameters.First(), lambda.Parameters.Skip(1).ToList().AsReadOnly());
// Return a new expression converter that uses the initialized command tree and binding context.
return new ExpressionConverter(funcletizer, lambda.Body);
}
/// <summary>
/// Replaces ParameterExpresion with ConstantExpression
/// to make the expression usable as a donor expression
/// </summary>
private sealed class CreateDonateableExpressionVisitor : EntityExpressionVisitor
{
private readonly Dictionary<ParameterExpression, object> _parameterToValueLookup;
private CreateDonateableExpressionVisitor(Dictionary<ParameterExpression, object> parameterToValueLookup)
{
_parameterToValueLookup = parameterToValueLookup;
}
internal static Expression Replace(LambdaExpression query, ObjectContext objectContext, object[] parameterValues)
{
Dictionary<ParameterExpression, object> parameterLookup = query
.Parameters
.Skip(1)
.Zip(parameterValues)
.ToDictionary(pair => pair.Key, pair => pair.Value);
parameterLookup.Add(query.Parameters.First(), objectContext);
var replacer = new CreateDonateableExpressionVisitor(parameterLookup);
return replacer.Visit(query.Body);
}
internal override Expression VisitParameter(ParameterExpression p)
{
object value;
Expression result;
if (_parameterToValueLookup.TryGetValue(p, out value))
{
result = Expression.Constant(value, p.Type);
}
else
{
result = base.VisitParameter(p);
}
return result;
}
}
}
}
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