might be NEEDED. ToParentDocValues uses advanceExact() of underneath DocValues [LUCENE-9360]

[asfimport]

Currently ToParentDocvalues.advanceExact() propagates it to DocValues.advance() as advised at #8922. It causes some problem at #10368 and seems not really reasonable. The later jira has patch attached which resolves this. The questions is why(not)?
cc @jpountz

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Migrated from LUCENE-9360 by Mikhail Khludnev (@mkhludnev), resolved Dec 18 2021
Parent: #10368

[asfimport]

Adrien Grand (@jpountz) (migrated from JIRA)

I looked at the Jira but it's not clean to me what the problem is with calling advance() under the hood, can you explain? I'm also a bit confused why the Jira has both patches and a PR attached, which do not have the same content, what would eventually get merged?

[asfimport]

Mikhail Khludnev (@mkhludnev) (migrated from JIRA)

@jpountz, I were rushing through test failures. Today #10368 tests have passed without change in ToParentDocValues. Attached the right patch to #10368, at least I think so.

[asfimport]

Mikhail Khludnev (@mkhludnev) (migrated from JIRA)

Turns out it's necessary, because #10368.patch fails https://builds.apache.org/job/PreCommit-LUCENE-Build/268/artifact/out/patch-unit-solr_core.txt

   [junit4] Suite: org.apache.solr.search.grouping.AllGroupHeadsCollectorTest
   [junit4]   2> 4047854 INFO  (SUITE-AllGroupHeadsCollectorTest-seed#[A8E569347CC3E5CE]-worker) [     ] o.a.s.SolrTestCase Setting 'solr.default.confdir' system property to test-framework derived value of '/home/jenkins/jenkins-slave/workspace/PreCommit-LUCENE-Build/sourcedir/solr/server/solr/configsets/_default/conf'
   [junit4]   2> NOTE: reproduce with: ant test  -Dtestcase=AllGroupHeadsCollectorTest -Dtests.method=testBasicBlockJoin -Dtests.seed=A8E569347CC3E5CE -Dtests.multiplier=2 -Dtests.slow=true -Dtests.locale=pa-Guru-IN -Dtests.timezone=Antarctica/South_Pole -Dtests.asserts=true -Dtests.file.encoding=UTF-8
   [junit4] FAILURE 0.12s J0 | AllGroupHeadsCollectorTest.testBasicBlockJoin <<<
   [junit4]    > Throwable #1: java.lang.AssertionError
   [junit4]    > 	at __randomizedtesting.SeedInfo.seed([A8E569347CC3E5CE:9E22703862079502]:0)
   [junit4]    > 	at org.apache.lucene.index.AssertingLeafReader$AssertingSortedDocValues.advance(AssertingLeafReader.java:757)
   [junit4]    > 	at org.apache.lucene.search.grouping.DocValuesPoolingReader$1.advance(DocValuesPoolingReader.java:127)
   [junit4]    > 	at org.apache.lucene.search.SortedSetSelector$MaxValue.advance(SortedSetSelector.java:186)
   [junit4]    > 	at org.apache.lucene.search.ConjunctionDISI.doNext(ConjunctionDISI.java:200)
   [junit4]    > 	at org.apache.lucene.search.ConjunctionDISI.advance(ConjunctionDISI.java:230)
   [junit4]    > 	at org.apache.lucene.search.join.ToParentDocValues.advanceExact(ToParentDocValues.java:259)
   [junit4]    > 	at org.apache.lucene.search.join.ToParentDocValues$SortedDVs.advanceExact(ToParentDocValues.java:84)
   [junit4]    > 	at org.apache.lucene.search.FieldComparator$TermOrdValComparator.getOrdForDoc(FieldComparator.java:643)
   [junit4]    > 	at org.apache.lucene.search.FieldComparator$TermOrdValComparator.copy(FieldComparator.java:691)
   [junit4]    > 	at org.apache.lucene.search.grouping.AllGroupHeadsCollector$SortingGroupHead.<init>(AllGroupHeadsCollector.java:278)
   [junit4]    > 	at org.apache.lucene.search.grouping.AllGroupHeadsCollector$SortingGroupHeadsCollector.newGroupHead(AllGroupHeadsCollector.java:260)
   [junit4]    > 	at org.apache.lucene.search.grouping.AllGroupHeadsCollector.collect(AllGroupHeadsCollector.java:137)
   [junit4]    > 	at org.apache.lucene.search.AssertingLeafCollector.collect(AssertingLeafCollector.java:49)
   [junit4]    > 	at org.apache.lucene.search.AssertingCollector$1.collect(AssertingCollector.java:58)
   [junit4]    > 	at org.apache.lucene.search.AssertingLeafCollector.collect(AssertingLeafCollector.java:49)
   [junit4]    > 	at org.apache.lucene.search.AssertingLeafCollector.collect(AssertingLeafCollector.java:49)
   [junit4]    > 	at org.apache.lucene.search.Weight$DefaultBulkScorer.scoreAll(Weight.java:254)
   [junit4]    > 	at org.apache.lucene.search.Weight$DefaultBulkScorer.score(Weight.java:205)
   [junit4]    > 	at org.apache.lucene.search.AssertingBulkScorer.score(AssertingBulkScorer.java:81)
   [junit4]    > 	at org.apache.lucene.search.AssertingBulkScorer.score(AssertingBulkScorer.java:65)
   [junit4]    > 	at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:741)
   [junit4]    > 	at org.apache.lucene.search.AssertingIndexSearcher.search(AssertingIndexSearcher.java:72)
   [junit4]    > 	at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:528)
   [junit4]    > 	at org.apache.solr.search.grouping.AllGroupHeadsCollectorTest.testBasicBlockJoin(AllGroupHeadsCollectorTest.java:150)

I'll check whether earlier fix with advanceExact() can heal it.

[asfimport]

Mikhail Khludnev (@mkhludnev) (migrated from JIRA)

what the problem is with calling advance() under the hood, can you explain

@jpountz, it turns out like this: let's we have parents docnums:10,20,30. While scoring 10th block child filter might jump to behind 20th block due to absent child docs. And then ToParentDocValues.advanceExact(20) will drag child field doc values back. It never happens in /master nor _8x now, but attempting to reuse docVals across Sorting Group Heads lead to this trouble.
#10368 provides a fix for it, but it a little bit fragile. Really appreciate your feedback. Thanks.

[asfimport]

Mikhail Khludnev (@mkhludnev) (migrated from JIRA)

will be addressed under enclosing issue