https://blog.csdn.net/whuqin/article/details/42524825

1.facet的直觀認識

facet：面、切面、方面。個人理解就是維度，在滿足query的前提下，觀察結果在各維度上的分布（一個維度下各子類的數目）。

如jd上搜“手機”，得到4009個商品。其中品牌、網絡、價格就是商品的維度(facet)，點擊某個品牌或者網絡，獲取更細分的結果。

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點擊品牌小米，獲得小米手機的結果，顯示27個。

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點擊移動4G，獲得移動4G、小米手機，顯示4個。

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2.facet特性

facet counting：返回一個facet下某子類的結果數。如上面的品牌維度下小米子類中滿足查詢"手機"的結果有27個。
facet associations：一個文檔與某子類的關聯度，如一本書30%講lucene，70%講solor，這個百分比就是書與分類的關聯度(匹配度、信心度)。
multiple facet requests：支持多facet查詢（多維度查詢）。如查詢品牌為小米、網絡為移動4G的手機。
3.實例

一個facet簡單使用例子，依賴于lucene-facet-4.10.0。講述了從搜手機到品牌、到網絡向下browser的過程。

public class SimpleFacetsExample {
private final Directory indexDir = new RAMDirectory();
private final Directory taxoDir = new RAMDirectory();
private final FacetsConfig config = new FacetsConfig();

/** Empty constructor */
public SimpleFacetsExample() {
config.setHierarchical("Publish Date", true);
}

/** Build the example index. */
private void index() throws IOException {
IndexWriter indexWriter = new IndexWriter(indexDir, new IndexWriterConfig(Version.LUCENE_4_10_0,
new WhitespaceAnalyzer()));
// Writes facet ords to a separate directory from the main index
DirectoryTaxonomyWriter taxoWriter = new DirectoryTaxonomyWriter(taxoDir);

Document doc = new Document();
doc.add(new TextField("device", "手機", Field.Store.YES));
doc.add(new TextField("name", "米1", Field.Store.YES));
doc.add(new FacetField("brand", "小米"));
doc.add(new FacetField("network", "移動4G"));
indexWriter.addDocument(config.build(taxoWriter, doc));

doc = new Document();
doc.add(new TextField("device", "手機", Field.Store.YES));
doc.add(new TextField("name", "米4", Field.Store.YES));
doc.add(new FacetField("brand", "小米"));
doc.add(new FacetField("network", "聯通4G"));
indexWriter.addDocument(config.build(taxoWriter, doc));

doc = new Document();
doc.add(new TextField("device", "手機", Field.Store.YES));
doc.add(new TextField("name", "榮耀6", Field.Store.YES));
doc.add(new FacetField("brand", "華為"));
doc.add(new FacetField("network", "移動4G"));
indexWriter.addDocument(config.build(taxoWriter, doc));

doc = new Document();
doc.add(new TextField("device", "電視", Field.Store.YES));
doc.add(new TextField("name", "小米電視2", Field.Store.YES));
doc.add(new FacetField("brand", "小米"));
indexWriter.addDocument(config.build(taxoWriter, doc));

taxoWriter.close();
indexWriter.close();
}

private void facetsWithSearch() throws IOException {
DirectoryReader indexReader = DirectoryReader.open(indexDir);
IndexSearcher searcher = new IndexSearcher(indexReader);
TaxonomyReader taxoReader = new DirectoryTaxonomyReader(taxoDir);

FacetsCollector fc = new FacetsCollector();
//1.查詢手機
System.out.println("-----手機-----");
TermQuery query = new TermQuery(new Term("device", "手機"));
FacetsCollector.search(searcher, query, 10, fc);
Facets facets = new FastTaxonomyFacetCounts(taxoReader, config, fc);
List<FacetResult> results = facets.getAllDims(10);
//手機總共有3個,品牌維度：小米2個，華為1個;網絡維度：移動4G 2個，聯通4G 1個
for (FacetResult tmp : results) {
System.out.println(tmp);
}
//2.drill down，品牌選小米
System.out.println("-----小米手機-----");
DrillDownQuery drillDownQuery = new DrillDownQuery(config, query);
drillDownQuery.add("brand", "小米");
FacetsCollector fc1 = new FacetsCollector();//要new新collector，否則會累加
FacetsCollector.search(searcher, drillDownQuery, 10, fc1);
facets = new FastTaxonomyFacetCounts(taxoReader, config, fc1);
results = facets.getAllDims(10);
//獲得小米手機的分布，總數2個，網絡：移動4G 1個，聯通4G 1個
for (FacetResult tmp : results) {
System.out.println(tmp);
}

//3.drill down，小米移動4G手機
System.out.println("-----移動4G小米手機-----");
drillDownQuery.add("network", "移動4G");
FacetsCollector fc2 = new FacetsCollector();
FacetsCollector.search(searcher, drillDownQuery, 10, fc2);
facets = new FastTaxonomyFacetCounts(taxoReader, config, fc2);
results = facets.getAllDims(10);
for (FacetResult tmp : results) {
System.out.println(tmp);
}

//4.drill sideways，橫向瀏覽
//如果已經進入了小米手機，但是還想看到其他牌子(華為)的手機數目，就用到了sideways
System.out.println("-----小米手機drill sideways-----");
DrillSideways ds = new DrillSideways(searcher, config, taxoReader);
DrillDownQuery drillDownQuery1 = new DrillDownQuery(config, query);
drillDownQuery1.add("brand", "小米");
DrillSidewaysResult result = ds.search(drillDownQuery1, 10);
results = result.facets.getAllDims(10);
for (FacetResult tmp : results) {
System.out.println(tmp);
}

indexReader.close();
taxoReader.close();
}

/** Runs the search and drill-down examples and prints the results. */
public static void main(String[] args) throws Exception {
SimpleFacetsExample example = new SimpleFacetsExample();
example.index();
example.facetsWithSearch();
}
}
輸出：

-----手機-----
//總數3個，2個子類
dim=brand path=[] value=3 childCount=2
小米 (2)
華為 (1)

dim=network path=[] value=3 childCount=2
移動4G (2)
聯通4G (1)

-----小米手機-----
//普通向下瀏覽，丟失了同一維度，其他子類的統計
dim=brand path=[] value=2 childCount=1
小米 (2)

dim=network path=[] value=2 childCount=2
移動4G (1)
聯通4G (1)

-----移動4G小米手機-----
dim=brand path=[] value=1 childCount=1
小米 (1)

dim=network path=[] value=1 childCount=1
移動4G (1)

-----小米手機drill sideways-----
//drill sideways, 保留了該drill維度的其他子類統計
dim=brand path=[] value=3 childCount=2
小米 (2)
華為 (1)
//小米手機中的網絡分布
dim=network path=[] value=2 childCount=2
移動4G (1)
聯通4G (1)

轉載于:https://www.cnblogs.com/davidwang456/p/10001465.html

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