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//---------------------------------------------------------------------
// <copyright file="ObjectFullSpanRewriter.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupowner Microsoft
//---------------------------------------------------------------------
namespace System.Data.Objects.Internal
{
using System.Collections.Generic;
using System.Data.Common.CommandTrees;
using System.Data.Common.CommandTrees.ExpressionBuilder;
using System.Data.Common.Utils;
using System.Data.Metadata.Edm;
using System.Diagnostics;
internal class ObjectFullSpanRewriter : ObjectSpanRewriter
{
/// <summary>
/// Represents a node in the 'Include' navigation property tree
/// built from the list of SpanPaths on the Span object with which
/// the FullSpanRewriter is constructed.
/// </summary>
private class SpanPathInfo
{
internal SpanPathInfo(EntityType declaringType)
{
this.DeclaringType = declaringType;
}
/// <summary>
/// The effective Entity type of this node in the tree
/// </summary>
internal EntityType DeclaringType;
/// <summary>
/// Describes the navigation properties that should be retrieved
/// from this node in the tree and the Include sub-paths that extend
/// from each of those navigation properties
/// </summary>
internal Dictionary<NavigationProperty, SpanPathInfo> Children;
}
/// <summary>
/// Maintains a reference to the SpanPathInfo tree node representing the
/// current position in the 'Include' path that is currently being expanded.
/// </summary>
private Stack<SpanPathInfo> _currentSpanPath = new Stack<SpanPathInfo>();
internal ObjectFullSpanRewriter(DbCommandTree tree, DbExpression toRewrite, Span span, AliasGenerator aliasGenerator)
: base(tree, toRewrite, aliasGenerator)
{
Debug.Assert(span != null, "Span cannot be null");
Debug.Assert(span.SpanList.Count > 0, "At least one span path is required");
// Retrieve the effective 'T' of the ObjectQuery<T> that produced
// the Command Tree that is being rewritten. This could be either
// literally 'T' or Collection<T>.
EntityType entityType = null;
if (!TryGetEntityType(this.Query.ResultType, out entityType))
{
// If the result type of the query is neither an Entity type nor a collection
// type with an Entity element type, then full Span is currently not allowed.
throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_IncludeRequiresEntityOrEntityCollection);
}
// Construct the SpanPathInfo navigation property tree using the
// list of Include Span paths from the Span object:
// Create a SpanPathInfo instance that represents the root of the tree
// and takes its Entity type from the Entity type of the result type of the query.
SpanPathInfo spanRoot = new SpanPathInfo(entityType);
// Populate the tree of navigation properties based on the navigation property names
// in the Span paths from the Span object. Commonly rooted span paths are merged, so
// that paths of "Customer.Order" and "Customer.Address", for example, will share a
// common SpanPathInfo for "Customer" in the Children collection of the root SpanPathInfo,
// and that SpanPathInfo will contain one child for "Order" and another for "Address".
foreach (Span.SpanPath path in span.SpanList)
{
AddSpanPath(spanRoot, path.Navigations);
}
// The 'current' span path is initialized to the root of the Include span tree
_currentSpanPath.Push(spanRoot);
}
/// <summary>
/// Populates the Include span tree with appropriate branches for the Include path
/// represented by the specified list of navigation property names.
/// </summary>
/// <param name="parentInfo">The root SpanPathInfo</param>
/// <param name="navPropNames">A list of navigation property names that describes a single Include span path</param>
private void AddSpanPath(SpanPathInfo parentInfo, List<string> navPropNames)
{
ConvertSpanPath(parentInfo, navPropNames, 0);
}
private void ConvertSpanPath(SpanPathInfo parentInfo, List<string> navPropNames, int pos)
{
// Attempt to retrieve the next navigation property from the current entity type
// using the name of the current navigation property in the Include path.
NavigationProperty nextNavProp = null;
if (!parentInfo.DeclaringType.NavigationProperties.TryGetValue(navPropNames[pos], true, out nextNavProp))
{
// The navigation property name is not valid for this Entity type
throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_NoNavProp(parentInfo.DeclaringType.FullName, navPropNames[pos]));
}
// The navigation property was retrieved, an entry for it must be ensured in the Children
// collection of the parent SpanPathInfo instance.
// If the parent's Children collection does not exist then instantiate it now:
if (null == parentInfo.Children)
{
parentInfo.Children = new Dictionary<NavigationProperty, SpanPathInfo>();
}
// If a sub-path that begins with the current navigation property name was already
// encountered, then a SpanPathInfo for this navigation property may already exist
// in the Children dictionary...
SpanPathInfo nextChild = null;
if (!parentInfo.Children.TryGetValue(nextNavProp, out nextChild))
{
// ... otherwise, create a new SpanPathInfo instance that this navigation
// property maps to and ensure its presence in the Children dictionary.
nextChild = new SpanPathInfo(EntityTypeFromResultType(nextNavProp));
parentInfo.Children[nextNavProp] = nextChild;
}
// If this navigation property is not the end of the span path then
// increment the position and recursively call ConvertSpanPath, specifying
// the (retrieved or newly-created) SpanPathInfo of this navigation property
// as the new 'parent' info.
if (pos < navPropNames.Count - 1)
{
ConvertSpanPath(nextChild, navPropNames, pos + 1);
}
}
/// <summary>
/// Retrieves the Entity (result or element) type produced by a Navigation Property.
/// </summary>
/// <param name="navProp">The navigation property</param>
/// <returns>
/// The Entity type produced by the navigation property.
/// This may be the immediate result type (if the result is at most one)
/// or the element type of the result type, otherwise.
/// </returns>
private static EntityType EntityTypeFromResultType(NavigationProperty navProp)
{
EntityType retType = null;
TryGetEntityType(navProp.TypeUsage, out retType);
// Currently, navigation properties may only return an Entity or Collection<Entity> result
Debug.Assert(retType != null, "Navigation property has non-Entity and non-Entity collection result type?");
return retType;
}
/// <summary>
/// Retrieves the Entity (result or element) type referenced by the specified TypeUsage, if
/// its EdmType is an Entity type or a collection type with an Entity element type.
/// </summary>
/// <param name="resultType">The TypeUsage that provides the EdmType to examine</param>
/// <param name="entityType">The referenced Entity (element) type, if present.</param>
/// <returns>
/// <c>true</c> if the specified <paramref name="resultType"/> is an Entity type or a
/// collection type with an Entity element type; otherwise <c>false</c>.
/// </returns>
private static bool TryGetEntityType(TypeUsage resultType, out EntityType entityType)
{
// If the result type is an Entity, then simply use that type.
if (BuiltInTypeKind.EntityType == resultType.EdmType.BuiltInTypeKind)
{
entityType = (EntityType)resultType.EdmType;
return true;
}
else if (BuiltInTypeKind.CollectionType == resultType.EdmType.BuiltInTypeKind)
{
// If the result type of the query is a collection, attempt to extract
// the element type of the collection and determine if it is an Entity type.
EdmType elementType = ((CollectionType)resultType.EdmType).TypeUsage.EdmType;
if (BuiltInTypeKind.EntityType == elementType.BuiltInTypeKind)
{
entityType = (EntityType)elementType;
return true;
}
}
entityType = null;
return false;
}
/// <summary>
/// Utility method to retrieve the 'To' AssociationEndMember of a NavigationProperty
/// </summary>
/// <param name="property">The navigation property</param>
/// <returns>The AssociationEndMember that is the target of the navigation operation represented by the NavigationProperty</returns>
private AssociationEndMember GetNavigationPropertyTargetEnd(NavigationProperty property)
{
AssociationType relationship = this.Metadata.GetItem<AssociationType>(property.RelationshipType.FullName, DataSpace.CSpace);
Debug.Assert(relationship.AssociationEndMembers.Contains(property.ToEndMember.Name), "Association does not declare member referenced by Navigation property?");
return relationship.AssociationEndMembers[property.ToEndMember.Name];
}
internal override SpanTrackingInfo CreateEntitySpanTrackingInfo(DbExpression expression, EntityType entityType)
{
SpanTrackingInfo tracking = new SpanTrackingInfo();
SpanPathInfo currentInfo = _currentSpanPath.Peek();
if (currentInfo.Children != null)
{
// The current SpanPathInfo instance on the top of the span path stack indicates
// which navigation properties should be retrieved from this Entity-typed expression
// and also specifies (in the form of child SpanPathInfo instances) which sub-paths
// must be expanded for each of those navigation properties.
// The SpanPathInfo instance may be the root instance or a SpanPathInfo that represents a sub-path.
int idx = 1; // SpanRoot is always the first (zeroth) column, full- and relationship-span columns follow.
foreach (KeyValuePair<NavigationProperty, SpanPathInfo> nextInfo in currentInfo.Children)
{
// If the tracking information was not initialized yet, do so now.
if (null == tracking.ColumnDefinitions)
{
tracking = InitializeTrackingInfo(this.RelationshipSpan);
}
// Create a property expression that retrieves the specified navigation property from the Entity-typed expression.
// Note that the expression is cloned since it may be used as the instance of multiple property expressions.
DbExpression columnDef = expression.Property(nextInfo.Key);
// Rewrite the result of the navigation property. This is required for two reasons:
// 1. To continue spanning the current Include path.
// 2. To apply relationship span to the Entity or EntityCollection produced by the navigation property, if necessary.
// Consider an Include path of "Order" for a query that returns OrderLines - the Include'd Orders should have
// their associated Customer relationship spanned.
// Note that this will recursively call this method with the Entity type of the result of the
// navigation property, which will in turn call loop through the sub-paths of this navigation
// property and adjust the stack to track which Include path is being expanded and which
// element of that path is considered 'current'.
_currentSpanPath.Push(nextInfo.Value);
columnDef = this.Rewrite(columnDef);
_currentSpanPath.Pop();
// Add a new column to the tracked columns using the rewritten column definition
tracking.ColumnDefinitions.Add(new KeyValuePair<string, DbExpression>(tracking.ColumnNames.Next(), columnDef));
AssociationEndMember targetEnd = GetNavigationPropertyTargetEnd(nextInfo.Key);
tracking.SpannedColumns[idx] = targetEnd;
// If full span and relationship span are both required, a relationship span may be rendered
// redundant by an already added full span. Therefore the association ends that have been expanded
// as part of full span are tracked using a dictionary.
if (this.RelationshipSpan)
{
tracking.FullSpannedEnds[targetEnd] = true;
}
idx++;
}
}
return tracking;
}
}
}
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