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// If a merge option was explicitly specified, and it does not match the plan's merge option, then the plan is no longer valid.
// If the context flag UseCSharpNullComparisonBehavior was modified, then the plan is no longer valid.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);
}
internal override ObjectQueryExecutionPlan GetExecutionPlan(MergeOption?forMergeOption)
{
// Metadata is required to generate the execution plan or to retrieve it from the cache.
this.ObjectContext.EnsureMetadata();
// Determine the required merge option, with the following precedence:
// 1. The merge option specified to Execute(MergeOption) as forMergeOption.
// 2. The merge option set via ObjectQuery.MergeOption.
// 3. The global default merge option.
MergeOption mergeOption = EnsureMergeOption(forMergeOption, this.UserSpecifiedMergeOption);
// If a cached plan is present, then it can be reused if it has the required merge option
// (since span and parameters cannot change between executions). However, if the cached
// plan does not have the required merge option we proceed as if it were not present.
ObjectQueryExecutionPlan plan = this._cachedPlan;
if (plan != null)
{
if (plan.MergeOption == mergeOption)
{
return(plan);
}
else
{
plan = null;
}
}
// There is no cached plan (or it was cleared), so the execution plan must be retrieved from
// the global query cache (if plan caching is enabled) or rebuilt for the required merge option.
QueryCacheManager cacheManager = null;
EntitySqlQueryCacheKey cacheKey = null;
if (this.PlanCachingEnabled)
{
// 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.
cacheKey = new EntitySqlQueryCacheKey(
this.ObjectContext.DefaultContainerName,
_queryText,
(null == this.Parameters ? 0 : this.Parameters.Count),
(null == this.Parameters ? null : this.Parameters.GetCacheKey()),
(null == this.Span ? null : this.Span.GetCacheKey()),
mergeOption,
this.ElementType);
cacheManager = this.ObjectContext.MetadataWorkspace.GetQueryCacheManager();
ObjectQueryExecutionPlan executionPlan = null;
if (cacheManager.TryCacheLookup(cacheKey, out executionPlan))
{
plan = executionPlan;
}
}
if (plan == null)
{
// Either caching is not enabled or the execution plan was not found in the cache
DbExpression queryExpression = this.Parse();
Debug.Assert(queryExpression != null, "EntitySqlQueryState.Parse returned null expression?");
DbQueryCommandTree tree = DbQueryCommandTree.FromValidExpression(this.ObjectContext.MetadataWorkspace, DataSpace.CSpace, queryExpression);
plan = ObjectQueryExecutionPlan.Prepare(this.ObjectContext, tree, this.ElementType, mergeOption, this.Span, null, DbExpressionBuilder.AliasGenerator);
// If caching is enabled then update the cache now.
// Note: the logic is the same as in ELinqQueryState.
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();
}
}
}
if (this.Parameters != null)
{
this.Parameters.SetReadOnly(true);
}
// Update the cached plan with the newly retrieved/prepared plan
this._cachedPlan = plan;
// Return the execution plan
return(plan);
}
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);
}