Lucene系列-facet

时间:2022-02-28 06:15:35

1.facet的直观认识

facet:面、切面、方面。个人理解就是维度,在满足query的前提下,观察结果在各维度上的分布(一个维度下各子类的数目)。

如jd上搜“手机”,得到4009个商品。其中品牌、网络、价格就是商品的维度(facet),点击某个品牌或者网络,获取更细分的结果。

Lucene系列-facet

点击品牌小米,获得小米手机的结果,显示27个。

Lucene系列-facet

点击移动4G,获得移动4G、小米手机,显示4个。

Lucene系列-facet

2.facet特性

  • facet counting:返回一个facet下某子类的结果数。如上面的品牌维度下小米子类中满足查询"手机"的结果有27个。
  • facet associations:一个文档与某子类的关联度,如一本书30%讲lucene,70%讲solor,这个百分比就是书与分类的关联度(匹配度、信心度)。
  • multiple facet requests:支持多facet查询(多维度查询)。如查询品牌为小米、网络为移动4G的手机。

3.实例

一个facet简单使用例子,依赖于lucene-facet-4.10.0。讲述了从搜手机到品牌、到网络向下browser的过程。

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", "手机", 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", "移动4G"));
indexWriter.addDocument(config.build(taxoWriter, doc)); doc = new Document();
doc.add(new TextField("device", "手机", 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", "联通4G"));
indexWriter.addDocument(config.build(taxoWriter, doc)); doc = new Document();
doc.add(new TextField("device", "手机", Field.Store.YES));
doc.add(new TextField("name", "荣耀6", Field.Store.YES));
doc.add(new FacetField("brand", "华为"));
doc.add(new FacetField("network", "移动4G"));
indexWriter.addDocument(config.build(taxoWriter, doc)); doc = new Document();
doc.add(new TextField("device", "电视", Field.Store.YES));
doc.add(new TextField("name", "小米电视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.查询手机
System.out.println("-----手机-----");
TermQuery query = new TermQuery(new Term("device", "手机"));
FacetsCollector.search(searcher, query, 10, fc);
Facets facets = new FastTaxonomyFacetCounts(taxoReader, config, fc);
List<FacetResult> results = facets.getAllDims(10);
//手机总共有3个,品牌维度:小米2个,华为1个;网络维度:移动4G 2个,联通4G 1个
for (FacetResult tmp : results) {
System.out.println(tmp);
}
//2.drill down,品牌选小米
System.out.println("-----小米手机-----");
DrillDownQuery drillDownQuery = new DrillDownQuery(config, query);
drillDownQuery.add("brand", "小米");
FacetsCollector fc1 = new FacetsCollector();//要new新collector,否则会累加
FacetsCollector.search(searcher, drillDownQuery, 10, fc1);
facets = new FastTaxonomyFacetCounts(taxoReader, config, fc1);
results = facets.getAllDims(10);
//获得小米手机的分布,总数2个,网络:移动4G 1个,联通4G 1个
for (FacetResult tmp : results) {
System.out.println(tmp);
} //3.drill down,小米移动4G手机
System.out.println("-----移动4G小米手机-----");
drillDownQuery.add("network", "移动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,横向浏览
//如果已经进入了小米手机,但是还想看到其他牌子(华为)的手机数目,就用到了sideways
System.out.println("-----小米手机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();
}
}

输出:

-----手机-----
//总数3个,2个子类
dim=brand path=[] value=3 childCount=2
小米 (2)
华为 (1) dim=network path=[] value=3 childCount=2
移动4G (2)
联通4G (1) -----小米手机-----
//普通向下浏览,丢失了同一维度,其他子类的统计
dim=brand path=[] value=2 childCount=1
小米 (2) dim=network path=[] value=2 childCount=2
移动4G (1)
联通4G (1) -----移动4G小米手机-----
dim=brand path=[] value=1 childCount=1
小米 (1) dim=network path=[] value=1 childCount=1
移动4G (1) -----小米手机drill sideways-----
//drill sideways, 保留了该drill维度的其他子类统计
dim=brand path=[] value=3 childCount=2
小米 (2)
华为 (1)
//小米手机中的网络分布
dim=network path=[] value=2 childCount=2
移动4G (1)
联通4G (1)