/// <summary>
/// Parses an order by expression.
/// Order by expression consists only of expression optionally followed by ASC or DESC token separated by comma.
/// OrderBy -> ORDER BY OrderTerm (, OrderTerm)*
/// OrderTerm -> Expression (ASC|DESC)?
/// </summary>
/// <returns> A tree representation of a order by or null if the tokens are missing order token on its first position. </returns>
static public OrderByNode ParseOrderBy(ref int position, List <Token> tokens)
{
OrderByNode orderByNode = new OrderByNode();
// We expect after reading match expr that the position is set on the Order token.
// ORDER
if (!CheckToken(position, Token.TokenType.Order, tokens))
{
return(null);
}
else
{
position++;
// BY
if (!CheckToken(position, Token.TokenType.By, tokens))
{
ThrowError("Order by parser", "Expected BY.", position, tokens);
}
else
{
position++;
}
Node node = ParseOrderTerm(ref position, tokens);
if (node == null)
{
ThrowError("Order by parser", "Expected order by term.", position, tokens);
}
orderByNode.AddNext(node);
return(orderByNode);
}
}
/// <summary>
/// The root of the parse tree.
/// Jumps to the node under the root.
/// </summary>
public void Visit(OrderByNode node)
{
node.next.Accept(this);
if (result.Count < 1)
{
throw new ArgumentException($"{ this.GetType()}, failed to parse select expr.");
}
}
public void Visit(OrderByNode node)
{
throw new NotImplementedException();
}
/// <summary>
/// Creates an order by object.
/// </summary>
/// <param name="graph"> A graph the query is computed on. </param>
/// <param name="variableMap"> A map of query variables. </param>
/// <param name="executionHelper"> An order by execution helper. </param>
/// <param name="orderByNode"> A parse tree of order by expression. </param>
/// <param name="exprInfo"> A query expression information. </param>
public OrderByObject(Graph graph, VariableMap variableMap, IOrderByExecutionHelper executionHelper, OrderByNode orderByNode, QueryExpressionInfo exprInfo)
{
if (executionHelper == null || orderByNode == null || variableMap == null || graph == null || exprInfo == null)
{
throw new ArgumentNullException($"{this.GetType()}, passing null arguments to the constructor.");
}
this.helper = executionHelper;
var orderByVisitor = new OrderByVisitor(graph.labels, variableMap, exprInfo);
orderByVisitor.Visit(orderByNode);
var comps = orderByVisitor.GetResult();
executionHelper.IsSetOrderBy = true;
this.comparers = comps.ToArray();
}
public static ExpressionComparer[] ParseOrderBy(Graph graph, VariableMap variableMap, IOrderByExecutionHelper executionHelper, OrderByNode orderByNode, QueryExpressionInfo exprInfo, int columnCount)
{
if (executionHelper == null || orderByNode == null || variableMap == null || graph == null || exprInfo == null)
{
throw new ArgumentNullException($"Order by result processor, passing null arguments to the constructor.");
}
var orderByVisitor = new OrderByVisitor(graph.labels, variableMap, exprInfo);
orderByVisitor.Visit(orderByNode);
var comps = orderByVisitor.GetResult();
executionHelper.IsSetOrderBy = true;
return(comps.ToArray());
}
