public Expression ExtractPolicy(Expression expression)
{
_isNoTracking = false;
IsSequenceType = false;
ElementType = expression.Type;
CachingPolicy = null;
if (expression.Type.IsSequenceType(out var elementType))
{
IsSequenceType = true;
ElementType = elementType;
}
expression = Visit(expression);
if (!_isNoTracking && typeof(BaseEntity).IsAssignableFrom(ElementType))
{
// We never gonna cache trackable entities
CachingPolicy = null;
}
else
{
CachingPolicy = SanitizePolicy(CachingPolicy);
}
return(expression);
}
public void TestDefaultImpl()
{
var plc = new DbCachingPolicy();
Assert.IsTrue(plc.CanBeCached(null));
Assert.IsTrue(plc.CanBeCached(null, 0));
Assert.AreEqual(TimeSpan.MaxValue, plc.GetExpirationTimeout(null));
Assert.AreEqual(DbCachingMode.ReadWrite, plc.GetCachingMode(null));
}
private DbCachingPolicy SanitizePolicy(DbCachingPolicy policy)
{
if (policy?.NoCaching == true)
{
// Caching disabled on query level
return(null);
}
// Try resolve global policy
var policyAttribute = GetAllEntityInfos().Get(ElementType)?.Policy;
if (policyAttribute != null)
{
if (policyAttribute.NeverCache)
{
return(null);
}
// Either create new policy from attribute or merge attribute with query policy.
policy = (policy ?? new DbCachingPolicy()).Merge(policyAttribute);
}
if (policy != null)
{
// Global fallbacks from extension options
if (policy.ExpirationTimeout == null)
{
policy.ExpirationTimeout = _extension.DefaultExpirationTimeout;
}
if (policy.MaxRows == null)
{
policy.MaxRows = _extension.DefaultMaxRows;
}
}
return(policy);
}
protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.Method.IsGenericMethod)
{
var methodDef = node.Method.GetGenericMethodDefinition();
// Find cachable query extension calls
if (methodDef == CachingQueryExtensions.AsCachingMethodInfo)
{
// Get parameter with "last one wins"
CachingPolicy = node.Arguments
.OfType <ConstantExpression>()
.Where(a => a.Value is DbCachingPolicy)
.Select(a => (DbCachingPolicy)a.Value)
.Last();
// Cut out extension expression
return(Visit(node.Arguments[0]));
}
else if (!_isNoTracking && (methodDef == CachingQueryExtensions.AsNoTrackingMethodInfo || methodDef == CachingQueryExtensions.AsNoTrackingWithIdentityResolutionMethodInfo))
{
// If _isNoTracking is true, we found the marker already. Useless to do it again.
if (node.Arguments.Count > 0)
{
var nodeType = node.Arguments[0]?.Type;
if (nodeType != null)
{
var nodeResultType = nodeType.GetGenericArguments()[0];
_isNoTracking = nodeResultType == ElementType;
}
}
}
}
return(base.VisitMethodCall(node));
}
