Examples of org.apache.lucene.search.join.BlockJoinCollector

org.apache.lucene.search.join.BlockJoinCollector
Collects parent document hits for a Query containing one more more BlockJoinQuery clauses, sorted by the specified parent Sort. Note that this cannot perform arbitrary joins; rather, it requires that all joined documents are indexed as a doc block (using {@link IndexWriter#addDocuments} or {@link IndexWriter#updateDocuments}). Ie, the join is computed at index time.
The parent Sort must only use fields from the parent documents; sorting by field in the child documents is not supported.

You should only use this collector if one or more of the clauses in the query is a {@link BlockJoinQuery}. This collector will find those query clauses and record the matching child documents for the top scoring parent documents.

Multiple joins (star join) and nested joins and a mix of the two are allowed, as long as in all cases the documents corresponding to a single row of each joined parent table were indexed as a doc block.

For the simple star join you can retrieve the {@link TopGroups} instance containing each {@link BlockJoinQuery}'s matching child documents for the top parent groups, using {@link #getTopGroups}. Ie, a single query, which will contain two or more {@link BlockJoinQuery}'s as clauses representing the star join, can then retrieve two or more {@link TopGroups} instances.
For nested joins, the query will run correctly (ie, match the right parent and child documents), however, because TopGroups is currently unable to support nesting (each group is not able to hold another TopGroups), you are only able to retrieve the TopGroups of the first join. The TopGroups of the nested joins will not be correct. See {@link org.apache.lucene.search.join} for a codesample. @lucene.experimental

    // Combine the parent and nested child queries into a single query for a candidate
    BooleanQuery fullQuery = new BooleanQuery();
    fullQuery.add(new BooleanClause(parentQuery, Occur.MUST));
    fullQuery.add(new BooleanClause(childJoinQuery, Occur.MUST));


    BlockJoinCollector c = new BlockJoinCollector(Sort.RELEVANCE, 1, true, false);


    s.search(fullQuery, c);
    
    TopGroups<Integer> results = c.getTopGroups(childJoinQuery, null, 0, 10, 0, true);


    //assertEquals(1, results.totalHitCount);
    assertEquals(1, results.totalGroupedHitCount);
    assertEquals(1, results.groups.length);

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            System.out.println();
          }
        }
      }
      
      final BlockJoinCollector c = new BlockJoinCollector(parentSort, 10, true, true);


      joinS.search(parentJoinQuery, c);


      final int hitsPerGroup = _TestUtil.nextInt(random, 1, 20);
      //final int hitsPerGroup = 100;
      final TopGroups<Integer> joinResults = c.getTopGroups(childJoinQuery, childSort, 0, hitsPerGroup, 0, true);


      if (VERBOSE) {
        System.out.println("\nTEST: block join index gets " + (joinResults == null ? 0 : joinResults.groups.length) + " groups; hitsPerGroup=" + hitsPerGroup);
        if (joinResults != null) {
          final GroupDocs<Integer>[] groups = joinResults.groups;

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    // Combine the parent and nested child queries into a single query for a candidate
    BooleanQuery fullQuery = new BooleanQuery();
    fullQuery.add(new BooleanClause(parentQuery, Occur.MUST));
    fullQuery.add(new BooleanClause(childJoinQuery, Occur.MUST));


    BlockJoinCollector c = new BlockJoinCollector(Sort.RELEVANCE, 1, true, false);


    s.search(fullQuery, c);
    
    TopGroups<Integer> results = c.getTopGroups(childJoinQuery, null, 0, 10, 0, true);


    //assertEquals(1, results.totalHitCount);
    assertEquals(1, results.totalGroupedHitCount);
    assertEquals(1, results.groups.length);

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            System.out.println();
          }
        }
      }
      
      final BlockJoinCollector c = new BlockJoinCollector(parentSort, 10, true, true);


      joinS.search(parentJoinQuery, c);


      final int hitsPerGroup = _TestUtil.nextInt(random, 1, 20);
      //final int hitsPerGroup = 100;
      final TopGroups<Integer> joinResults = c.getTopGroups(childJoinQuery, childSort, 0, hitsPerGroup, 0, true);


      if (VERBOSE) {
        System.out.println("\nTEST: block join index gets " + (joinResults == null ? 0 : joinResults.groups.length) + " groups; hitsPerGroup=" + hitsPerGroup);
        if (joinResults != null) {
          final GroupDocs<Integer>[] groups = joinResults.groups;

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    fullQuery.add(new BooleanClause(parentQuery, Occur.MUST));
    fullQuery.add(new BooleanClause(childJobJoinQuery, Occur.MUST));
    fullQuery.add(new BooleanClause(childQualificationJoinQuery, Occur.MUST));


    //????? How do I control volume of jobs vs qualifications per parent?
    BlockJoinCollector c = new BlockJoinCollector(Sort.RELEVANCE, 10, true, false);


    s.search(fullQuery, c);


    //Examine "Job" children
    boolean showNullPointerIssue=true;
    if (showNullPointerIssue) {
      TopGroups<Integer> jobResults = c.getTopGroups(childJobJoinQuery, null, 0, 10, 0, true);


      //assertEquals(1, results.totalHitCount);
      assertEquals(1, jobResults.totalGroupedHitCount);
      assertEquals(1, jobResults.groups.length);


      final GroupDocs<Integer> group = jobResults.groups[0];
      assertEquals(1, group.totalHits);


      Document childJobDoc = s.doc(group.scoreDocs[0].doc);
      //System.out.println("  doc=" + group.scoreDocs[0].doc);
      assertEquals("java", childJobDoc.get("skill"));
      assertNotNull(group.groupValue);
      Document parentDoc = s.doc(group.groupValue);
      assertEquals("Lisa", parentDoc.get("name"));
    }


    //Now Examine qualification children
    TopGroups<Integer> qualificationResults = c.getTopGroups(childQualificationJoinQuery, null, 0, 10, 0, true);


    //!!!!! This next line can null pointer - but only if prior "jobs" section called first
    assertEquals(1, qualificationResults.totalGroupedHitCount);
    assertEquals(1, qualificationResults.groups.length);

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Related Classes of org.apache.lucene.search.join.BlockJoinCollector

org.apache.lucene.search.ScoreCachingWrappingScorer

org.apache.lucene.search.TestBlockJoin

org.apache.lucene.search.TopDocs

org.apache.lucene.search.TopDocsCollector

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