[jira] [Commented] (LUCENE-7255) Paging with SortingMergePolicy and EarlyTerminatingSortingCollector

["Christine Poerschke (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-7255?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15257870#comment-15257870 ] 

Christine Poerschke commented on LUCENE-7255:
---------------------------------------------

Hi [~adelapena] -  thanks for the report and code to reproduce.

I haven't yet tried to add your code to the existing [TestEarlyTerminatingSortingCollector|https://github.com/apache/lucene-solr/blob/master/lucene/misc/src/test/org/apache/lucene/search/TestEarlyTerminatingSortingCollector.java] tests but from just reading the code think that a higher {{numDocsToCollect}} argument might need to be passed to the [EarlyTerminatingSortingCollector|https://github.com/apache/lucene-solr/blob/master/lucene/misc/src/java/org/apache/lucene/search/EarlyTerminatingSortingCollector.java] constructor i.e.

{code}
- EarlyTerminatingSortingCollector collector = new EarlyTerminatingSortingCollector(tfc, sort, pageSize, sort);
+ EarlyTerminatingSortingCollector collector = new EarlyTerminatingSortingCollector(tfc, sort, numToSkip+pageSize, sort);
{code}

Is that something you could try out when you have a few minutes? This could make a good additional TestEarlyTerminatingSortingCollector test I think.




> Paging with SortingMergePolicy and EarlyTerminatingSortingCollector
> -------------------------------------------------------------------
>
>                 Key: LUCENE-7255
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7255
>             Project: Lucene - Core
>          Issue Type: Bug
>    Affects Versions: 5.3, 5.4, 5.5, 6.0
>            Reporter: Andrés de la Peña
>              Labels: EarlyTerminatingSortingCollector, pagination, paging, searchafter, sortingmergepolicy
>
> {{EarlyTerminatingSortingCollector}} seems to don't work when used with a {{TopDocsCollector}} searching for documents after a certain {{FieldDoc}}. That is, it can't be used for paging. The following code allows to reproduce the problem:
> {code}
> // Sort to be used both with merge policy and queries
> Sort sort = new Sort(new SortedNumericSortField(FIELD_NAME, SortField.Type.INT));
> // Create directory
> RAMDirectory directory = new RAMDirectory();
> // Setup merge policy
> TieredMergePolicy tieredMergePolicy = new TieredMergePolicy();
> SortingMergePolicy sortingMergePolicy = new SortingMergePolicy(tieredMergePolicy, sort);
> // Setup index writer
> IndexWriterConfig indexWriterConfig = new IndexWriterConfig(new SimpleAnalyzer());
> indexWriterConfig.setOpenMode(IndexWriterConfig.OpenMode.CREATE_OR_APPEND);
> indexWriterConfig.setMergePolicy(sortingMergePolicy);
> IndexWriter indexWriter = new IndexWriter(directory, indexWriterConfig);
> // Index values
> for (int i = 1; i <= 1000; i++) {
>     Document document = new Document();
>     document.add(new NumericDocValuesField(FIELD_NAME, i));
>     indexWriter.addDocument(document);
> }
> // Force index merge to ensure early termination
> indexWriter.forceMerge(1, true);
> indexWriter.commit();
> // Create index searcher
> IndexReader reader = DirectoryReader.open(directory);
> IndexSearcher searcher = new IndexSearcher(reader);
> // Paginated read
> int pageSize = 10;
> FieldDoc pageStart = null;
> while (true) {
>     logger.info("Collecting page starting at: {}", pageStart);
>     Query query = new MatchAllDocsQuery();
>     TopDocsCollector tfc = TopFieldCollector.create(sort, pageSize, pageStart, true, false, false);
>     EarlyTerminatingSortingCollector collector = new EarlyTerminatingSortingCollector(tfc, sort, pageSize, sort);
>     searcher.search(query, collector);
>     ScoreDoc[] scoreDocs = tfc.topDocs().scoreDocs;
>     for (ScoreDoc scoreDoc : scoreDocs) {
>         pageStart = (FieldDoc) scoreDoc;
>         logger.info("FOUND {}", scoreDoc);
>     }
>     logger.info("Terminated early: {}", collector.terminatedEarly());
>     if (scoreDocs.length < pageSize) break;
> }
> // Close
> reader.close();
> indexWriter.close();
> directory.close();
> {code}
> The query for the second page doesn't return any results. However, it gets the expected results when if we don't wrap the {{TopFieldCollector}} with the {{EarlyTerminatingSortingCollector}}.



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