import org.apache.lucene.search.grouping.AbstractGroupFacetCollector; //导入依赖的package包/类
/**
 * Groups variations from specified {@link List} of {@link VcfFile}s by specified field
 * @param files a {@link List} of {@link FeatureFile}, which indexes to search
 * @param query a query to search in index
 * @param groupBy a field to perform grouping
 * @return a {@link List} of {@link Group}s, mapping field value to number of variations, having this value
 * @throws IOException if something goes wrong with the file system
 */
public List<Group> groupVariations(List<VcfFile> files, Query query, String groupBy) throws IOException {
    List<Group> res = new ArrayList<>();

    if (CollectionUtils.isEmpty(files)) {
        return Collections.emptyList();
    }

    SimpleFSDirectory[] indexes = fileManager.getIndexesForFiles(files);

    try (MultiReader reader = openMultiReader(indexes)) {
        if (reader.numDocs() == 0) {
            return Collections.emptyList();
        }

        IndexSearcher searcher = new IndexSearcher(reader);
        AbstractGroupFacetCollector groupedFacetCollector =
            TermGroupFacetCollector.createTermGroupFacetCollector(FeatureIndexFields.UID.fieldName,
                                                  getGroupByField(files, groupBy), false, null, GROUP_INITIAL_SIZE);
        searcher.search(query, groupedFacetCollector); // Computing the grouped facet counts
        TermGroupFacetCollector.GroupedFacetResult groupedResult = groupedFacetCollector.mergeSegmentResults(
            reader.numDocs(), 1, false);
        List<AbstractGroupFacetCollector.FacetEntry> facetEntries = groupedResult.getFacetEntries(0,
                                                                                                  reader.numDocs());
        for (AbstractGroupFacetCollector.FacetEntry facetEntry : facetEntries) {
            res.add(new Group(facetEntry.getValue().utf8ToString(), facetEntry.getCount()));
        }
    } finally {
        for (SimpleFSDirectory index : indexes) {
            IOUtils.closeQuietly(index);
        }
    }

    return res;
}
 

import org.apache.lucene.search.grouping.AbstractGroupFacetCollector; //导入依赖的package包/类
/**
 * Groups variations from specified {@link List} of {@link VcfFile}s by specified field
 * @param files a {@link List} of {@link FeatureFile}, which indexes to search
 * @param query a query to search in index
 * @param groupBy a field to perform grouping
 * @return a {@link List} of {@link Group}s, mapping field value to number of variations, having this value
 * @throws IOException if something goes wrong with the file system
 */
public List<Group> groupVariations(List<VcfFile> files, Query query, String groupBy) throws IOException {
    List<Group> res = new ArrayList<>();

    if (CollectionUtils.isEmpty(files)) {
        return Collections.emptyList();
    }

    SimpleFSDirectory[] indexes = fileManager.getIndexesForFiles(files);
    long totalIndexSize = getTotalIndexSize(indexes);
    if (totalIndexSize > luceneIndexMaxSizeForGrouping) {
        throw new IllegalArgumentException(getMessage(MessagesConstants.ERROR_FEATURE_INEDX_TOO_LARGE));
    }

    try (MultiReader reader = openMultiReader(indexes)) {
        if (reader.numDocs() == 0) {
            return Collections.emptyList();
        }

        IndexSearcher searcher = new IndexSearcher(reader);
        AbstractGroupFacetCollector groupedFacetCollector =
                TermGroupFacetCollector.createTermGroupFacetCollector(FeatureIndexFields.UID.fieldName,
                        getGroupByField(files, groupBy), false, null, GROUP_INITIAL_SIZE);
        searcher.search(query, groupedFacetCollector); // Computing the grouped facet counts
        TermGroupFacetCollector.GroupedFacetResult groupedResult = groupedFacetCollector.mergeSegmentResults(
                reader.numDocs(), 1, false);
        List<AbstractGroupFacetCollector.FacetEntry> facetEntries = groupedResult.getFacetEntries(0,
                reader.numDocs());
        for (AbstractGroupFacetCollector.FacetEntry facetEntry : facetEntries) {
            res.add(new Group(facetEntry.getValue().utf8ToString(), facetEntry.getCount()));
        }
    } finally {
        for (SimpleFSDirectory index : indexes) {
            IOUtils.closeQuietly(index);
        }
    }

    return res;
}