/// <summary>
/// Prepares the join tree
/// </summary>
private JoinTree PrepareJoin()
{
// construct the join tree
var allPaths = new List <string[]>();
if (Select != null)
{
allPaths.AddRange(Select.Select(e => e.Path));
}
if (Filter != null)
{
allPaths.AddRange(Filter.Select(e => e.Path));
}
// This will represent the mapping from paths to symbols
var joinTree = JoinTree.Make(ResultType, allPaths);
return(joinTree);
}
/// <summary>
/// Create the <see cref="JoinTree"/> from the paths in all the arguments
/// </summary>
private JoinTree PrepareJoin(ArraySegment <string>?pathToCollection = null)
{
// construct the join tree
var allPaths = new List <string[]>();
if (Select != null)
{
allPaths.AddRange(Select.Select(e => e.Path));
}
if (Expand != null)
{
allPaths.AddRange(Expand.Select(e => e.Path));
}
if (Filter != null)
{
allPaths.AddRange(Filter.Select(e => e.Path));
}
if (OrderBy != null)
{
allPaths.AddRange(OrderBy.Select(e => e.Path));
}
if (pathToCollection != null)
{
var pathToCollectionEntity = new ArraySegment <string>(
pathToCollection.Value.Array,
pathToCollection.Value.Offset,
pathToCollection.Value.Count - 1);
allPaths.Add(pathToCollectionEntity.ToArray());
}
// This will represent the mapping from paths to symbols
return(JoinTree.Make(ResultType, allPaths));
}
/// <summary>
/// Prepares the SELECT statement and the column map, using the <see cref="Select"/> argument
/// </summary>
private SqlSelectClause PrepareSelect(JoinTree joinTree)
{
var selects = new HashSet <(string Symbol, string PropName)>();
var columns = new List <(string Symbol, ArraySegment <string> Path, string PropName)>();
void AddSelect(string symbol, ArraySegment <string> path, string propName)
{
// NULL happens when there is a select that has been segmented from the middle
// and the first section of the segment no longer terminates with a simple property
// propName = propName ?? "Id";
if (propName == null)
{
return;
}
if (selects.Add((symbol, propName)))
{
columns.Add((symbol, path, propName));
}
}
// Any path step that is touched by a select (which has a property) ignores the expand, the joinTree below
// allows us to efficiently check if any particular step is touched by a select
JoinTree overridingSelectTree = Select == null ? null : JoinTree.Make(ResultType, Select.Select(e => e.Path)); // Overriding select paths
// Optimization: remember the joins that have been selected and don't select them again
HashSet <JoinTree> selectedJoins = new HashSet <JoinTree>();
// For every expanded entity that has not been tainted by a select argument, we add all its properties to the list of selects
Expand ??= ExpandExpression.Empty;
foreach (var expand in Expand.Union(ExpandExpression.RootSingleton))
{
string[] path = expand.Path;
for (int i = 0; i <= path.Length; i++)
{
var subpath = new ArraySegment <string>(path, 0, i);
var selectMatch = overridingSelectTree?[subpath];
if (selectMatch == null) // This expand is not overridden by a select
{
var join = joinTree[subpath];
if (join == null)
{
// Developer mistake
throw new InvalidOperationException($"The path '{string.Join('/', subpath)}' was not found in the joinTree");
}
else if (selectedJoins.Contains(join))
{
continue;
}
else
{
selectedJoins.Add(join);
}
foreach (var prop in join.Type.GetMappedProperties())
{
AddSelect(join.Symbol, subpath, prop.Name);
}
}
}
}
if (Select != null)
{
foreach (var select in Select)
{
// Add the property
string[] path = select.Path;
{
var join = joinTree[path];
var propName = select.Property; // Can be null
AddSelect(join.Symbol, path, propName);
}
// In this loop we ensure all levels to the selected properties
// have their Ids and Foreign Keys added to the select collection
for (int i = 0; i <= path.Length; i++)
{
var subpath = new ArraySegment <string>(path, 0, i);
var join = joinTree[subpath];
if (join == null)
{
// Developer mistake
throw new InvalidOperationException($"The path '{string.Join('/', subpath)}' was not found in the joinTree");
}
else if (selectedJoins.Contains(join))
{
// All properties were added earlier in an expand
continue;
}
else
{
selectedJoins.Add(join);
}
// The Id is ALWAYS required in every EntityWithKey
if (join.Type.IsSubclassOf(typeof(EntityWithKey)))
{
AddSelect(join.Symbol, subpath, "Id");
}
// Add all the foreign keys to the next level down
foreach (var nextJoin in join.Values)
{
AddSelect(join.Symbol, subpath, nextJoin.ForeignKeyName);
}
}
}
}
// If the foreign key to the principal query is specified, then always include that
// otherwise there will be no way to link the collection to the principal query once we load the data
if (!string.IsNullOrWhiteSpace(ForeignKeyToPrincipalQuery))
{
var path = new string[0];
AddSelect(joinTree.Symbol, path, ForeignKeyToPrincipalQuery);
}
// Deals with trees
foreach (var path in PathsToParentEntitiesWithExpandedAncestors)
{
var join = joinTree[path];
AddSelect(join.Symbol, path, "ParentId");
}
if (IsAncestorExpand)
{
var path = new string[0];
AddSelect(joinTree.Symbol, path, "ParentId");
}
// Change the hash set to a list so that the order is well defined
return(new SqlSelectClause(columns));
}
