// Helper method to compute expression joins
private JoinedMapResult CreateJoinedMap(Resource property, GraphExpression expression)
{
var joinSegment = new LabelledTreeNode <object, Term>(Root).AddChild(property, expression.Root);
var joineMapComparisonSites = new List <JoinAddressPair> {
new JoinAddressPair {
TreeAddress1 = new List <Term> {
property
}, TreeAddress2 = new List <Term>()
}
};
IMap joinedMap = new JoinMap(new BgpMap(joinSegment), expression.Map, joineMapComparisonSites);
var comparisonSites = new List <JoinAddressPair> {
JoinAddressPair.RootComparison
};
return(new JoinedMapResult {
Map = joinedMap, AddressPairList = comparisonSites
});
}
/// <summary>
/// Left Join
/// </summary>
/// <param name="property"></param>
/// <param name="expression"></param>
/// <returns></returns>
public GraphExpression LeftJoin(Resource property, GraphExpression expression)
{
var result = CreateJoinedMap(property, expression);
return(new GraphExpression(new LeftJoinMap(Map, result.Map, result.AddressPairList)));
}
/// <summary>
/// Execute the query codified in the graph expression on the source
/// </summary>
/// <returns>A collection of graph results that match the graph expression</returns>
public IEnumerable <LabelledTreeNode <object, Term> > Execute(GraphExpression graphExpression, IGraphSource source = null)
{
return(graphExpression.Map.Evaluate <T>(source ?? DefaultSource));
}
/// <summary>
/// Union
/// </summary>
/// <param name="graphExpression"></param>
/// <returns></returns>
public GraphExpression Union(GraphExpression graphExpression)
{
return(new GraphExpression(new UnionMap(Map, graphExpression.Map)));
}
/// <summary>
/// Expands the graph expression with the specified property and query.
/// The new graph expression will bind a given context if and only if both the old expression and the addition bind
/// </summary>
/// <param name="property">property along which to expand</param>
/// <param name="query">queryable graph required at the end of the property</param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Require(Resource property, IQueryableGraph query)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Join(property, query.GraphExpression)));
}
/// <summary>
/// Expands the graph expression with the specified property and terminal object, the return the terminal object
/// The new graph expression will bind a given context if and only if both the old expression and the addition bind
/// </summary>
/// <param name="property">property along which to expand</param>
/// <param name="object">object required at the end of the property, can be left null to insert a variable</param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Select(Resource property, Term @object = null)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Select(property, @object)));
}
/// <summary>
/// Expands the graph expression with the specified property and object.
/// The new graph expression will bind a given context if and only if both the old expression and the addition bind
/// </summary>
/// <param name="property">property along which to expand</param>
/// <param name="object">object required at the end of the property, can be left null to insert a variable</param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Require(Resource property, Term @object = null)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Join(property, @object)));
}
/// <summary>
/// Returns an instance of a QueryableGraph
/// </summary>
/// <param name="graphExpression">codifies the query to be executed</param>
/// <param name="graphProvider">manages the translation of graph expression to generic graph query result</param>
public QueryableGraph(IGraphProvider graphProvider, GraphExpression graphExpression = null)
{
GraphProvider = graphProvider;
GraphExpression = graphExpression ?? GraphExpression.Empty;
}
/// <summary>
/// Returns the first count bindings
/// </summary>
/// <param name="count">maximum number of elements to return</param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Limit(int count)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Slice(null, count)));
}
/// <summary>
/// Returns the union of two queries, the graph expressions are left unaltered.
/// </summary>
/// <param name="query"></param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Union(IQueryableGraph query)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Union(query.GraphExpression)));
}
/// <summary>
/// Expands the graph expression with the specified property and terminal query, then return the terminal query
/// The new graph expression will bind a given context if and only if both the old expression and the addition bind
/// </summary>
/// <param name="property">property along which to expand</param>
/// <param name="query">queryable graph required at the end of the property</param>
/// <returns>a queryable graph</returns>
public IQueryableGraph Select(Resource property, IQueryableGraph query)
{
return(new QueryableGraph(GraphProvider, GraphExpression.Select(property, query.GraphExpression)));
}
