|
//------------------------------------------------------------------------------
// <copyright file="Coordinator.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Globalization;
using System.Data.Objects.Internal;
namespace System.Data.Common.Internal.Materialization
{
/// <summary>
/// A coordinator is responsible for tracking state and processing result in a root or nested query
/// result collection. The coordinator exists within a graph, and knows its Parent, (First)Child,
/// and Next sibling. This allows the Shaper to use the coordinator as a simple state machine when
/// consuming store reader results.
/// </summary>
internal abstract class Coordinator
{
#region state
/// <summary>
/// The factory used to generate this coordinator instance. Contains delegates used
/// by the Shaper during result enumeration.
/// </summary>
internal readonly CoordinatorFactory CoordinatorFactory;
/// <summary>
/// Parent coordinator (the coordinator producing rows containing this collection).
/// If this is the root, null.
/// </summary>
internal readonly Coordinator Parent;
/// <summary>
/// First coordinator for nested results below this collection. When reading a new row
/// for this coordinator, we walk down to the Child.
///
/// NOTE:: this cannot be readonly because we can't know both the parent and the child
/// at initialization time; we set the Child in the parent's constructor.
/// </summary>
public Coordinator Child
{
get { return _child; }
protected set { _child = value; }
}
private Coordinator _child;
/// <summary>
/// Next coordinator at this depth. Once we're done consuming results for this reader,
/// we move on to this.Next.
/// </summary>
internal readonly Coordinator Next;
/// <summary>
/// Indicates whether data has been read for the collection being aggregated or yielded
/// by this coordinator.
/// </summary>
public bool IsEntered
{
get { return _isEntered; }
protected set { _isEntered = value; }
}
private bool _isEntered;
/// <summary>
/// Indicates whether this is the top level coordinator for a query.
/// </summary>
internal bool IsRoot
{
get { return null == Parent; }
}
#endregion
#region constructor
protected Coordinator(CoordinatorFactory coordinatorFactory, Coordinator parent, Coordinator next)
{
this.CoordinatorFactory = coordinatorFactory;
this.Parent = parent;
this.Next = next;
}
#endregion
#region "public" surface area
/// <summary>
/// Registers this hierarchy of coordinators in the given shaper.
/// </summary>
internal void Initialize(Shaper shaper)
{
ResetCollection(shaper);
// Add this coordinator to the appropriate state slot in the
// shaper so that it is available to materialization delegates.
shaper.State[this.CoordinatorFactory.StateSlot] = this;
if (null != this.Child)
{
this.Child.Initialize(shaper);
}
if (null != this.Next)
{
this.Next.Initialize(shaper);
}
}
/// <summary>
/// Determines the maximum depth of this subtree.
/// </summary>
internal int MaxDistanceToLeaf()
{
int maxDistance = 0;
Coordinator child = this.Child;
while (null != child)
{
maxDistance = Math.Max(maxDistance, child.MaxDistanceToLeaf() + 1);
child = child.Next;
}
return maxDistance;
}
/// <summary>
/// This method is called when the current collection is finished and it's time to move to the next collection.
/// Recursively initializes children and siblings as well.
/// </summary>
internal abstract void ResetCollection(Shaper shaper);
/// <summary>
/// Precondition: the current row has data for the coordinator.
/// Side-effects: updates keys currently stored in state and updates IsEntered if a new value is encountered.
/// Determines whether the row contains the next element in this collection.
/// </summary>
internal bool HasNextElement(Shaper shaper)
{
// check if this row contains a new element for this coordinator
bool result = false;
if (!this.IsEntered || !this.CoordinatorFactory.CheckKeys(shaper))
{
// remember initial keys values
this.CoordinatorFactory.SetKeys(shaper);
this.IsEntered = true;
result = true;
}
return result;
}
/// <summary>
/// Precondition: the current row has data and contains a new element for the coordinator.
/// Reads the next element in this collection.
/// </summary>
internal abstract void ReadNextElement(Shaper shaper);
#endregion
}
/// <summary>
/// Typed <see cref="Coordinator"/>
/// </summary>
internal class Coordinator<T> : Coordinator
{
#region state
internal readonly CoordinatorFactory<T> TypedCoordinatorFactory;
/// <summary>
/// Exposes the Current element that has been materialized (and is being populated) by this coordinator.
/// </summary>
internal T Current
{
get { return _current; }
}
private T _current;
/// <summary>
/// For ObjectResult, aggregates all elements for in the nested collection handled by this coordinator.
/// </summary>
private ICollection<T> _elements;
/// <summary>
/// For ObjectResult, aggregates all elements as wrapped entities for in the nested collection handled by this coordinator.
/// </summary>
private List<IEntityWrapper> _wrappedElements;
/// <summary>
/// Delegate called when the current nested collection has been consumed. This is necessary in Span
/// scenarios where an EntityCollection RelatedEnd is populated only when all related entities have
/// been materialized. This version of the close handler works with wrapped entities.
/// </summary>
private Action<Shaper, List<IEntityWrapper>> _handleClose;
/// <summary>
/// For nested, object-layer coordinators we want to collect all the elements we find and handle them
/// when the root coordinator advances. Otherwise we just want to return them as we find them.
/// </summary>
private readonly bool IsUsingElementCollection;
#endregion
#region constructors
internal Coordinator(CoordinatorFactory<T> coordinator, Coordinator parent, Coordinator next)
: base(coordinator, parent, next)
{
this.TypedCoordinatorFactory = coordinator;
// generate all children
Coordinator nextChild = null;
foreach (var nestedCoordinator in coordinator.NestedCoordinators.Reverse())
{
// last child processed is first child...
this.Child = nestedCoordinator.CreateCoordinator(this, nextChild);
nextChild = this.Child;
}
this.IsUsingElementCollection = (!this.IsRoot && typeof(T) != typeof(RecordState));
}
#endregion
#region "public" surface area
internal override void ResetCollection(Shaper shaper)
{
// Check to see if anyone has registered for notification when the current coordinator
// is reset.
if (null != _handleClose)
{
_handleClose(shaper, _wrappedElements);
_handleClose = null;
}
// Reset is entered for this collection.
this.IsEntered = false;
if (IsUsingElementCollection)
{
_elements = this.TypedCoordinatorFactory.InitializeCollection(shaper);
_wrappedElements = new List<IEntityWrapper>();
}
if (null != this.Child)
{
this.Child.ResetCollection(shaper);
}
if (null != this.Next)
{
this.Next.ResetCollection(shaper);
}
}
internal override void ReadNextElement(Shaper shaper)
{
T element;
IEntityWrapper wrappedElement = null;
try
{
if (this.TypedCoordinatorFactory.WrappedElement == null)
{
element = this.TypedCoordinatorFactory.Element(shaper);
}
else
{
wrappedElement = this.TypedCoordinatorFactory.WrappedElement(shaper);
// This cast may throw, in which case it will be immediately caught
// and the error handling expression will be used to get the appropriate error message.
element = (T)wrappedElement.Entity;
}
}
catch (Exception e)
{
if (EntityUtil.IsCatchableExceptionType(e))
{
// Some errors can occur while a close handler is registered. This clears
// out the handler so that ElementWithErrorHandling will report the correct
// error rather than asserting on the missing close handler.
ResetCollection(shaper);
// call a variation of the "Element" delegate with more detailed
// error handling (to produce a better exception message)
element = this.TypedCoordinatorFactory.ElementWithErrorHandling(shaper);
}
// rethrow
throw;
}
if (IsUsingElementCollection)
{
_elements.Add(element);
if (wrappedElement != null)
{
_wrappedElements.Add(wrappedElement);
}
}
else
{
_current = element;
}
}
/// <summary>
/// Sets the delegate called when this collection is closed. This close handler works on
/// a collection of wrapped entities, rather than on the raw entity objects.
/// </summary>
internal void RegisterCloseHandler(Action<Shaper, List<IEntityWrapper>> closeHandler)
{
Debug.Assert(null == _handleClose, "more than one handler for a collection close 'event'");
_handleClose = closeHandler;
}
/// <summary>
/// Called when we're disposing the enumerator;
/// </summary>
internal void SetCurrentToDefault()
{
_current = default(T);
}
#endregion
#region runtime callable code
// Code in this section is called from the delegates produced by the Translator. It may
// not show up if you search using Find All References
/// <summary>
/// Returns a handle to the element aggregator for this nested collection.
/// </summary>
private IEnumerable<T> GetElements()
{
return _elements;
}
#endregion
}
}
|