/// <summary>
/// Applies a <see cref="ExpressionSelect"/> on the <see cref="Query{T}"/> to determine what columns need to be returned
/// </summary>
public Query <T> Select(ExpressionSelect select)
{
var clone = Clone();
clone._select = select;
return(clone);
}
/// <summary>
/// A version of <see cref="Select(ExpressionSelect)"/> that accepts a string
/// </summary>
public Query <T> Select(string select)
{
return(Select(ExpressionSelect.Parse(select)));
}
/// <summary>
/// Backbone for <see cref="CountAsync(CancellationToken, int)"/>, <see cref="ToListAsync(CancellationToken)"/> and <see cref="ToListAndCountAsync(CancellationToken)"/>
/// </summary>
private async Task <(List <T> result, int count)> ToListAndCountInnerAsync(bool includeCount, int maxCount, CancellationToken cancellation)
{
var args = await _factory(cancellation);
var conn = args.Connection;
var sources = args.Sources;
var userId = args.UserId;
var userToday = args.UserToday;
var localizer = args.Localizer;
var i = args.Instrumentation;
var logger = args.Logger;
using var _ = i.Block("Query.ToListAndCountInnerAsync");
IDisposable block;
block = i.Block("Get Descriptor");
var resultDesc = TypeDescriptor.Get <T>();
block.Dispose();
block = i.Block("Validate Paths and Props");
_orderby ??= (IsEntityWithKey() ? ExpressionOrderBy.Parse("Id desc") :
throw new InvalidOperationException($"Query<{resultDesc.Type.Name}> was executed without an orderby clause"));
// Prepare all the query parameters
ExpressionSelect selectExp = _select;
ExpressionExpand expandExp = _expand;
ExpressionOrderBy orderbyExp = _orderby;
ExpressionFilter filterExp = _filterConditions?.Aggregate(
(e1, e2) => ExpressionFilter.Conjunction(e1, e2));
// To prevent SQL injection
ValidatePathsAndProperties(selectExp, expandExp, filterExp, orderbyExp, resultDesc, localizer);
// ------------------------ Step #1
block.Dispose();
block = i.Block("Prepare QueryInternals");
// Segment the paths of select and expand along the one-to-many relationships, each one-to-many relationship will
// result in a new internal query for the child collection with the original query as its principal query
var segments = new Dictionary <ArraySegment <string>, QueryInternal>(new PathEqualityComparer());
// Helper method for creating a an internal query, will be used later in both the select and the expand loops
QueryInternal MakeFlatQuery(ArraySegment <string> previousFullPath, ArraySegment <string> subPath, TypeDescriptor desc)
{
QueryInternal principalQuery = previousFullPath == null ? null : segments[previousFullPath];
ArraySegment <string> pathToCollectionPropertyInPrincipal = previousFullPath == null ? null : subPath;
if (principalQuery != null && desc.KeyType == KeyType.None)
{
// Programmer mistake
throw new InvalidOperationException($"[Bug] Type {desc.Name} has no Id property, yet it is used as a navigation collection on another entity");
}
string foreignKeyToPrincipalQuery = null;
bool isAncestorExpand = false;
if (principalQuery != null)
{
// This loop retrieves the entity descriptor that has the collection property
TypeDescriptor collectionPropertyEntity = principalQuery.ResultDescriptor;
int i = 0;
for (; i < pathToCollectionPropertyInPrincipal.Count - 1; i++)
{
var step = pathToCollectionPropertyInPrincipal[i];
collectionPropertyEntity = collectionPropertyEntity.NavigationProperty(step).TypeDescriptor;
}
// Get the collection/Parent property
string propertyName = pathToCollectionPropertyInPrincipal[i];
var property = collectionPropertyEntity.Property(propertyName);
if (property is NavigationPropertyDescriptor navProperty && navProperty.IsParent)
{
foreignKeyToPrincipalQuery = "ParentId";
isAncestorExpand = true;
}
else if (property is CollectionPropertyDescriptor collProperty)
{
// Must be a collection then
foreignKeyToPrincipalQuery = collProperty.ForeignKeyName;
}
else
{
throw new InvalidOperationException($"Bug: Segment along a property {property.Name} on type {collectionPropertyEntity.Name} That is neither a collection nor a parent");
}
}
if (isAncestorExpand)
{
// the path to parent entity is the path above minus the "Parent"
var pathToParentEntity = new ArraySegment <string>(
array: pathToCollectionPropertyInPrincipal.Array,
offset: 0,
count: pathToCollectionPropertyInPrincipal.Count - 1);
// Adding this causes the principal query to always include ParentId in the select clause
principalQuery.PathsToParentEntitiesWithExpandedAncestors.Add(pathToParentEntity);
}
// This is the orderby of related queries, and the default orderby of the root query
var defaultOrderBy = ExpressionOrderBy.Parse(
desc.HasProperty("Index") ? "Index" :
desc.HasProperty("SortKey") ? "SortKey" : "Id");
// Prepare the flat query and return it
var flatQuery = new QueryInternal
{
PrincipalQuery = principalQuery,
IsAncestorExpand = isAncestorExpand,
PathToCollectionPropertyInPrincipal = pathToCollectionPropertyInPrincipal,
ForeignKeyToPrincipalQuery = foreignKeyToPrincipalQuery,
ResultDescriptor = desc,
OrderBy = defaultOrderBy
};
return(flatQuery);
}