/// <summary>
/// Create the single pass collector.
/// </summary>
/// <param name="groupSort">
/// The <see cref="Sort"/> used to sort the
/// groups. The top sorted document within each group
/// according to groupSort, determines how that group
/// sorts against other groups. This must be non-null,
/// ie, if you want to groupSort by relevance use
/// <see cref="Sort.RELEVANCE"/>.
/// </param>
/// <param name="topNGroups">How many top groups to keep.</param>
/// <param name="needsScores">
/// true if the collected documents
/// require scores, either because relevance is included
/// in the withinGroupSort or because you plan to pass true
/// for either GetScores or GetMaxScores to <see cref="GetTopGroups(Sort, int, int, int, bool)"/>
/// </param>
/// <param name="lastDocPerGroup">
/// a <see cref="Filter"/> that marks the
/// last document in each group.
/// </param>
public BlockGroupingCollector(Sort groupSort, int topNGroups, bool needsScores, Filter lastDocPerGroup)
{
if (topNGroups < 1)
{
throw new ArgumentOutOfRangeException(nameof(topNGroups), "topNGroups must be >= 1 (got " + topNGroups + ")"); // LUCENENET specific - changed from IllegalArgumentException to ArgumentOutOfRangeException (.NET convention)
}
groupQueue = new GroupQueue(this, topNGroups);
pendingSubDocs = new int[10];
if (needsScores)
{
pendingSubScores = new float[10];
}
this.needsScores = needsScores;
this.lastDocPerGroup = lastDocPerGroup;
// TODO: allow null groupSort to mean "by relevance",
// and specialize it?
this.groupSort = groupSort;
this.topNGroups = topNGroups;
SortField[] sortFields = groupSort.GetSort();
comparers = new FieldComparer[sortFields.Length];
compIDXEnd = comparers.Length - 1;
reversed = new int[sortFields.Length];
for (int i = 0; i < sortFields.Length; i++)
{
SortField sortField = sortFields[i];
comparers[i] = sortField.GetComparer(topNGroups, i);
reversed[i] = sortField.IsReverse ? -1 : 1;
}
}
