|
//---------------------------------------------------------------------
// <copyright file="ELinqQueryState.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.Data.Common.CommandTrees;
using System.Data.Common.CommandTrees.Internal;
using System.Data.Common.QueryCache;
using System.Data.Metadata.Edm;
using System.Data.Objects;
using System.Data.Objects.ELinq;
using System.Data.Objects.Internal;
using System.Diagnostics;
using System.Reflection;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.ObjectModel;
/// <summary>
/// Models a Linq to Entities ObjectQuery
/// </summary>
internal class ELinqQueryState : ObjectQueryState
{
#region Private State
private readonly Expression _expression;
private Func<bool> _recompileRequired;
private ReadOnlyCollection<KeyValuePair<ObjectParameter, QueryParameterExpression>> _linqParameters;
private bool _useCSharpNullComparisonBehavior;
#endregion
#region Constructors
/// <summary>
/// Constructs a new <see cref="ELinqQueryState"/> instance based on the specified Linq Expression
/// against the specified ObjectContext.
/// </summary>
/// <param name="elementType">The element type of the implemented ObjectQuery, as a CLR type.</param>
/// <param name="context">The ObjectContext with which the implemented ObjectQuery is associated.</param>
/// <param name="expression">The Linq Expression that defines this query.</param>
internal ELinqQueryState(Type elementType, ObjectContext context, Expression expression)
: base(elementType, context, null, null)
{
//
// Initialize the LINQ expression, which is passed in via
// public APIs on ObjectQuery and must be checked here
// (the base class performs similar checks on the ObjectContext and MergeOption arguments).
//
EntityUtil.CheckArgumentNull(expression, "expression");
// closure bindings and initializers are explicitly allowed to be null
_expression = expression;
_useCSharpNullComparisonBehavior = context.ContextOptions.UseCSharpNullComparisonBehavior;
}
/// <summary>
/// Constructs a new <see cref="ELinqQueryState"/> instance based on the specified Linq Expression,
/// copying the state information from the specified ObjectQuery.
/// </summary>
/// <param name="elementType">The element type of the implemented ObjectQuery, as a CLR type.</param>
/// <param name="query">The ObjectQuery from which the state information should be copied.</param>
/// <param name="expression">The Linq Expression that defines this query.</param>
internal ELinqQueryState(Type elementType, ObjectQuery query, Expression expression)
: base(elementType, query)
{
EntityUtil.CheckArgumentNull(expression, "expression");
_expression = expression;
}
#endregion
#region ObjectQueryState overrides
protected override TypeUsage GetResultType()
{
// Since this method is only called once, on demand, a full conversion pass
// is performed to produce the DbExpression and return its result type.
// This does not affect any cached execution plan or closure bindings that may be present.
ExpressionConverter converter = this.CreateExpressionConverter();
return converter.Convert().ResultType;
}
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?");
// If this query has already been prepared, its current execution plan may no longer be valid.
ObjectQueryExecutionPlan plan = this._cachedPlan;
if (plan != null)
{
// Was a merge option specified in the call to Execute(MergeOption) or set via ObjectQuery.MergeOption?
MergeOption? explicitMergeOption = GetMergeOption(forMergeOption, this.UserSpecifiedMergeOption);
// If a merge option was explicitly specified, and it does not match the plan's merge option, then the plan is no longer valid.
// If the context flag UseCSharpNullComparisonBehavior was modified, then the plan is no longer valid.
if((explicitMergeOption.HasValue &&
explicitMergeOption.Value != plan.MergeOption) ||
this._recompileRequired() ||
this.ObjectContext.ContextOptions.UseCSharpNullComparisonBehavior != this._useCSharpNullComparisonBehavior)
{
plan = null;
}
}
// The plan may have been invalidated above, or this query may never have been prepared.
if (plan == null)
{
// Metadata is required to generate the execution plan.
this.ObjectContext.EnsureMetadata();
// Reset internal state
this._recompileRequired = null;
this.ResetParameters();
// Translate LINQ expression to a DbExpression
ExpressionConverter converter = this.CreateExpressionConverter();
DbExpression queryExpression = converter.Convert();
// This delegate tells us when a part of the expression tree has changed requiring a recompile.
this._recompileRequired = converter.RecompileRequired;
// Determine the merge option, with the following precedence:
// 1. A merge option was specified explicitly as the argument to Execute(MergeOption).
// 2. The user has set the MergeOption property on the ObjectQuery instance.
// 3. A merge option has been extracted from the 'root' query and propagated to the root of the expression tree.
// 4. The global default merge option.
MergeOption mergeOption = EnsureMergeOption(forMergeOption,
this.UserSpecifiedMergeOption,
converter.PropagatedMergeOption);
this._useCSharpNullComparisonBehavior = this.ObjectContext.ContextOptions.UseCSharpNullComparisonBehavior;
// If parameters were aggregated from referenced (non-LINQ) ObjectQuery instances then add them to the parameters collection
_linqParameters = converter.GetParameters();
if (_linqParameters != null && _linqParameters.Count > 0)
{
ObjectParameterCollection currentParams = this.EnsureParameters();
currentParams.SetReadOnly(false);
foreach (KeyValuePair<ObjectParameter, QueryParameterExpression> pair in _linqParameters)
{
// Note that it is safe to add the parameter directly only
// because parameters are cloned before they are added to the
// converter's parameter collection, or they came from this
// instance's parameter collection in the first place.
ObjectParameter convertedParam = pair.Key;
currentParams.Add(convertedParam);
}
currentParams.SetReadOnly(true);
}
// Try retrieving the execution plan from the global query cache (if plan caching is enabled).
System.Data.Common.QueryCache.QueryCacheManager cacheManager = null;
System.Data.Common.QueryCache.LinqQueryCacheKey cacheKey = null;
if (this.PlanCachingEnabled && !this._recompileRequired())
{
// Create a new cache key that reflects the current state of the Parameters collection
// and the Span object (if any), and uses the specified merge option.
string expressionKey;
if (ExpressionKeyGen.TryGenerateKey(queryExpression, out expressionKey))
{
cacheKey = new System.Data.Common.QueryCache.LinqQueryCacheKey(
expressionKey,
(null == this.Parameters ? 0 : this.Parameters.Count),
(null == this.Parameters ? null : this.Parameters.GetCacheKey()),
(null == converter.PropagatedSpan ? null : converter.PropagatedSpan.GetCacheKey()),
mergeOption,
this._useCSharpNullComparisonBehavior,
this.ElementType);
cacheManager = this.ObjectContext.MetadataWorkspace.GetQueryCacheManager();
ObjectQueryExecutionPlan executionPlan = null;
if (cacheManager.TryCacheLookup(cacheKey, out executionPlan))
{
plan = executionPlan;
}
}
}
// If execution plan wasn't retrieved from the cache, build a new one and cache it.
if (plan == null)
{
DbQueryCommandTree tree = DbQueryCommandTree.FromValidExpression(this.ObjectContext.MetadataWorkspace, DataSpace.CSpace, queryExpression);
plan = ObjectQueryExecutionPlan.Prepare(this.ObjectContext, tree, this.ElementType, mergeOption, converter.PropagatedSpan, null, converter.AliasGenerator);
// If caching is enabled then update the cache now.
// Note: the logic is the same as in EntitySqlQueryState.
if (cacheKey != null)
{
var newEntry = new QueryCacheEntry(cacheKey, plan);
QueryCacheEntry foundEntry = null;
if (cacheManager.TryLookupAndAdd(newEntry, out foundEntry))
{
// If TryLookupAndAdd returns 'true' then the entry was already present in the cache when the attempt to add was made.
// In this case the existing execution plan should be used.
plan = (ObjectQueryExecutionPlan)foundEntry.GetTarget();
}
}
}
// Remember the current plan in the local cache, so that we don't have to recalc the key and look into the global cache
// if the same instance of query gets executed more than once.
this._cachedPlan = plan;
}
// Evaluate parameter values for the query.
if (_linqParameters != null)
{
foreach (KeyValuePair<ObjectParameter, QueryParameterExpression> pair in _linqParameters)
{
ObjectParameter parameter = pair.Key;
QueryParameterExpression parameterExpression = pair.Value;
if (null != parameterExpression)
{
parameter.Value = parameterExpression.EvaluateParameter(null);
}
}
}
return plan;
}
/// <summary>
/// Returns a new ObjectQueryState instance with the specified navigation property path specified as an Include span.
/// For eLINQ queries the Include operation is modelled as a method call expression applied to the source ObectQuery,
/// so the <see cref="Span"/> property is always <c>null</c> on the returned instance.
/// </summary>
/// <typeparam name="TElementType">The element type of the resulting query</typeparam>
/// <param name="sourceQuery">The ObjectQuery on which Include was called; required to build the new method call expression</param>
/// <param name="includePath">The new Include path</param>
/// <returns>A new ObjectQueryState instance that incorporates the Include path, in this case a new method call expression</returns>
internal override ObjectQueryState Include<TElementType>(ObjectQuery<TElementType> sourceQuery, string includePath)
{
MethodInfo includeMethod = sourceQuery.GetType().GetMethod("Include", BindingFlags.Public | BindingFlags.Instance);
Debug.Assert(includeMethod != null, "Unable to find ObjectQuery.Include method?");
Expression includeCall = Expression.Call(Expression.Constant(sourceQuery), includeMethod, new Expression[] { Expression.Constant(includePath, typeof(string)) });
ObjectQueryState retState = new ELinqQueryState(this.ElementType, this.ObjectContext, includeCall);
this.ApplySettingsTo(retState);
return retState;
}
/// <summary>
/// eLINQ queries do not have command text. This method always returns <c>false</c>.
/// </summary>
/// <param name="commandText">Always set to <c>null</c></param>
/// <returns>Always returns <c>false</c></returns>
internal override bool TryGetCommandText(out string commandText)
{
commandText = null;
return false;
}
/// <summary>
/// Gets the LINQ Expression that defines this query for external (of ObjectQueryState) use.
/// Note that the <see cref="Expression"/> property is used, which is overridden by compiled eLINQ
/// queries to produce an Expression tree where parameter references have been replaced with constants.
/// </summary>
/// <param name="expression">The LINQ expression that describes this query</param>
/// <returns>Always returns <c>true</c></returns>
internal override bool TryGetExpression(out System.Linq.Expressions.Expression expression)
{
expression = this.Expression;
return true;
}
#endregion
internal virtual Expression Expression { get { return _expression; } }
protected virtual ExpressionConverter CreateExpressionConverter()
{
Funcletizer funcletizer = Funcletizer.CreateQueryFuncletizer(this.ObjectContext);
return new ExpressionConverter(funcletizer, _expression);
}
private void ResetParameters()
{
if (this.Parameters != null)
{
bool wasLocked = ((ICollection<ObjectParameter>)this.Parameters).IsReadOnly;
if (wasLocked)
{
this.Parameters.SetReadOnly(false);
}
this.Parameters.Clear();
if (wasLocked)
{
this.Parameters.SetReadOnly(true);
}
}
_linqParameters = null;
}
}
}
|