query  time join  已经在solr存在一段时间了但是lucene中有这个终归是好事，多一种选择嘛，实现这种关联的document还是很实用的，可以实现部分关联查询；

更新属性的时候也可以设计好结构，更新部分索引了。

这个解释有点费劲，还是看代码吧，

1. final String idField = "id";
2. +    final String toField = "productId";
3. +
4. +    Directory dir = newDirectory();
5. +    RandomIndexWriter w = new RandomIndexWriter(
6. +        random,
7. +        dir,
8. +        newIndexWriterConfig(TEST_VERSION_CURRENT,
9. +            new MockAnalyzer(random)).setMergePolicy(newLogMergePolicy()));
10. +
11. +    // 0
12. +    Document doc = new Document();
13. +    doc.add(new Field("description", "random text", TextField.TYPE_STORED));
14. +    doc.add(new Field("name", "name1", TextField.TYPE_STORED));
15. +    doc.add(new Field(idField, "1", TextField.TYPE_STORED));
16. +    w.addDocument(doc);
17. +
18. +    // 1
19. +    doc = new Document();
20. +    doc.add(new Field("price", "10.0", TextField.TYPE_STORED));
21. +    doc.add(new Field(idField, "2", TextField.TYPE_STORED));
22. +    doc.add(new Field(toField, "1", TextField.TYPE_STORED));
23. +    w.addDocument(doc);
24. +
25. +    // 2
26. +    doc = new Document();
27. +    doc.add(new Field("price", "20.0", TextField.TYPE_STORED));
28. +    doc.add(new Field(idField, "3", TextField.TYPE_STORED));
29. +    doc.add(new Field(toField, "1", TextField.TYPE_STORED));
30. +    w.addDocument(doc);
31. +
32. +    // 3
33. +    doc = new Document();
34. +    doc.add(new Field("description", "more random text", TextField.TYPE_STORED));
35. +    doc.add(new Field("name", "name2", TextField.TYPE_STORED));
36. +    doc.add(new Field(idField, "4", TextField.TYPE_STORED));
37. +    w.addDocument(doc);
38. +    w.commit();
39. +
40. +    // 4
41. +    doc = new Document();
42. +    doc.add(new Field("price", "10.0", TextField.TYPE_STORED));
43. +    doc.add(new Field(idField, "5", TextField.TYPE_STORED));
44. +    doc.add(new Field(toField, "4", TextField.TYPE_STORED));
45. +    w.addDocument(doc);
46. +
47. +    // 5
48. +    doc = new Document();
49. +    doc.add(new Field("price", "20.0", TextField.TYPE_STORED));
50. +    doc.add(new Field(idField, "6", TextField.TYPE_STORED));
51. +    doc.add(new Field(toField, "4", TextField.TYPE_STORED));
52. +    w.addDocument(doc);
53. +
54. +    IndexSearcher indexSearcher = new IndexSearcher(w.getReader());
55. +    w.close();
56. +
57. +    // Search for product
58. +    Query joinQuery =
59. +        JoinUtil.createJoinQuery(idField, false, toField, new TermQuery(new Term("name", "name2")), indexSearcher);
60. +
61. +    TopDocs result = indexSearcher.search(joinQuery, 10);
62. +    assertEquals(2, result.totalHits);
63. +    assertEquals(4, result.scoreDocs[0].doc);
64. +    assertEquals(5, result.scoreDocs[1].doc);

上面的

JoinUtil.createJoinQuery(idField, false, toField, new TermQuery(new Term("name", "name2")), indexSearcher);

是lucene4.0中的，现在还是alphe版本，

在3.6中没有第二个boolean参数，据说4.0的要比3.6的 query  time join快3倍，没验证过。