/// <summary>
/// Uses the provided
/// <see cref="Lucene.Net.Queries.Function.ValueSource">Lucene.Net.Queries.Function.ValueSource
/// </see>
/// to assign second
/// pass scores.
/// </summary>
public ExpressionRescorer(Expression expression, Bindings bindings)
: base(new Sort
(expression.GetSortField(bindings, true)))
{
this.expression = expression;
this.bindings = bindings;
}
internal ExpressionValueSource(Bindings bindings, Expression expression)
{
if (bindings == null)
{
throw new ArgumentNullException();
}
if (expression == null)
{
throw new ArgumentNullException();
}
this.expression = expression;
variables = new ValueSource[expression.variables.Length];
bool needsScores = false;
for (int i = 0; i < variables.Length; i++)
{
ValueSource source = bindings.GetValueSource(expression.variables[i]);
if (source is ScoreValueSource)
{
needsScores = true;
}
else
{
var valueSource = source as ExpressionValueSource;
if (valueSource != null)
{
if (valueSource.NeedsScores())
{
needsScores = true;
}
}
else
{
if (source == null)
{
throw new SystemException("Internal error. Variable (" + expression.variables[i]
+ ") does not exist.");
}
}
}
variables[i] = source;
}
this.needsScores = needsScores;
}
/// <summary>Get a sort field which can be used to rank documents by this expression.
/// </summary>
/// <remarks>Get a sort field which can be used to rank documents by this expression.
/// </remarks>
public virtual SortField GetSortField(Bindings bindings, bool reverse)
{
return GetValueSource(bindings).GetSortField(reverse);
}
/// <summary>
/// Get a
/// <see cref="Lucene.Net.Search.Rescorer">Lucene.Net.Search.Rescorer</see>
/// , to rescore first-pass hits
/// using this expression.
/// </summary>
public virtual Rescorer GetRescorer(Bindings bindings)
{
return new ExpressionRescorer(this, bindings);
}
/// <summary>Get a value source which can compute the value of this expression in the context of the given bindings.
/// </summary>
/// <remarks>Get a value source which can compute the value of this expression in the context of the given bindings.
/// </remarks>
/// <param name="bindings">Bindings to use for external values in this expression</param>
/// <returns>A value source which will evaluate this expression when used</returns>
public virtual ValueSource GetValueSource(Bindings bindings)
{
return new ExpressionValueSource(bindings, this);
}
