/// <summary>
/// Returns the update or query view for an Extent as a
/// string.
/// There are a series of steps that we go through for discovering a view for an extent.
/// To start with we assume that we are working with Generated Views. To find out the
/// generated view we go to the ObjectItemCollection and see if it is not-null. If the ObjectItemCollection
/// is non-null, we get the view generation assemblies that it might have cached during the
/// Object metadata discovery.If there are no view generation assemblies we switch to the
/// runtime view generation strategy. If there are view generation assemblies, we get the list and
/// go through them and see if there are any assemblies that are there from which we have not already loaded
/// the views. We collect the views from assemblies that we have not already collected from earlier.
/// If the ObjectItemCollection is null and we are in the view generation mode, that means that
/// the query or update is issued from the Value layer and this is the first time view has been asked for.
/// The compile time view gen for value layer queries will work for very simple scenarios.
/// If the users wants to get the performance benefit, they should call MetadataWorkspace.LoadFromAssembly.
/// At this point we go through the referenced assemblies of the entry assembly( this wont work for Asp.net
/// or if the viewgen assembly was not referenced by the executing application).
/// and try to see if there were any view gen assemblies. If there are, we collect the views for all extents.
/// Once we have all the generated views gathered, we try to get the view for the extent passed in.
/// If we find one we will return it. If we can't find one an exception will be thrown.
/// If there were no view gen assemblies either in the ObjectItemCollection or in the list of referenced
/// assemblies of calling assembly, we change the mode to runtime view generation and will continue to
/// be in that mode for the rest of the lifetime of the mapping item collection.
/// </summary>
internal GeneratedView GetGeneratedView(EntitySetBase extent, MetadataWorkspace workspace, StorageMappingItemCollection storageMappingItemCollection)
{
//First check if we have collected a view from user-defined query views
//Dont need to worry whether to generate Query view or update viw, because that is relative to the extent.
GeneratedView view;
if (TryGetUserDefinedQueryView(extent, out view))
{
return(view);
}
//If this is a foreign key association, manufacture a view on the fly.
if (extent.BuiltInTypeKind == BuiltInTypeKind.AssociationSet)
{
AssociationSet aSet = (AssociationSet)extent;
if (aSet.ElementType.IsForeignKey)
{
if (m_config.IsViewTracing)
{
Helpers.StringTraceLine(String.Empty);
Helpers.StringTraceLine(String.Empty);
Helpers.FormatTraceLine("================= Generating FK Query View for: {0} =================", aSet.Name);
Helpers.StringTraceLine(String.Empty);
Helpers.StringTraceLine(String.Empty);
}
// Although we expose a collection of constraints in the API, there is only ever one constraint.
Debug.Assert(aSet.ElementType.ReferentialConstraints.Count == 1, "aSet.ElementType.ReferentialConstraints.Count == 1");
ReferentialConstraint rc = aSet.ElementType.ReferentialConstraints.Single();
EntitySet dependentSet = aSet.AssociationSetEnds[rc.ToRole.Name].EntitySet;
EntitySet principalSet = aSet.AssociationSetEnds[rc.FromRole.Name].EntitySet;
DbExpression qView = dependentSet.Scan();
// Introduce an OfType view if the dependent end is a subtype of the entity set
EntityType dependentType = MetadataHelper.GetEntityTypeForEnd((AssociationEndMember)rc.ToRole);
EntityType principalType = MetadataHelper.GetEntityTypeForEnd((AssociationEndMember)rc.FromRole);
if (dependentSet.ElementType.IsBaseTypeOf(dependentType))
{
qView = qView.OfType(TypeUsage.Create(dependentType));
}
if (rc.FromRole.RelationshipMultiplicity == RelationshipMultiplicity.ZeroOrOne)
{
// Filter out instances with existing relationships.
qView = qView.Where(e =>
{
DbExpression filter = null;
foreach (EdmProperty fkProp in rc.ToProperties)
{
DbExpression notIsNull = e.Property(fkProp).IsNull().Not();
filter = null == filter ? notIsNull : filter.And(notIsNull);
}
return(filter);
});
}
qView = qView.Select(e =>
{
List <DbExpression> ends = new List <DbExpression>();
foreach (AssociationEndMember end in aSet.ElementType.AssociationEndMembers)
{
if (end.Name == rc.ToRole.Name)
{
var keyValues = new List <KeyValuePair <string, DbExpression> >();
foreach (EdmMember keyMember in dependentSet.ElementType.KeyMembers)
{
keyValues.Add(e.Property((EdmProperty)keyMember));
}
ends.Add(dependentSet.RefFromKey(DbExpressionBuilder.NewRow(keyValues), dependentType));
}
else
{
// Manufacture a key using key values.
var keyValues = new List <KeyValuePair <string, DbExpression> >();
foreach (EdmMember keyMember in principalSet.ElementType.KeyMembers)
{
int offset = rc.FromProperties.IndexOf((EdmProperty)keyMember);
keyValues.Add(e.Property(rc.ToProperties[offset]));
}
ends.Add(principalSet.RefFromKey(DbExpressionBuilder.NewRow(keyValues), principalType));
}
}
return(TypeUsage.Create(aSet.ElementType).New(ends));
});
return(GeneratedView.CreateGeneratedViewForFKAssociationSet(aSet, aSet.ElementType, new DbQueryCommandTree(workspace, DataSpace.SSpace, qView), storageMappingItemCollection, m_config));
}
}
// If no User-defined QV is found, call memoized View Generation procedure.
Dictionary <EntitySetBase, GeneratedView> generatedViews = m_generatedViewsMemoizer.Evaluate(extent.EntityContainer);
if (!generatedViews.TryGetValue(extent, out view))
{
throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.Mapping_Views_For_Extent_Not_Generated(
(extent.EntityContainer.DataSpace == DataSpace.SSpace)?"Table":"EntitySet", extent.Name));
}
return(view);
}
