[LUCENE-10500] StringValueFacetCounts relies on sequential collection

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 9.2
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Luca Cavanna
• Created: 05/Apr/22 19:41
• Updated: 28/Aug/22 16:38
• Resolved: 06/Apr/22 07:45

Description

We recently moved some of the facets tests to use IndexSearcher#search(Query, CollectorManager) providing a FacetsCollectorManager instead of a FacetsCollector. Whenever newIndexSearcher(IndexReader) is used in tests, concurrent search may now be exercised while it was not before.

This caused some build failures on TestStringValueFacetCounts:

java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
	at __randomizedtesting.SeedInfo.seed([ED8BF8281FCE5C02:9FC7DD27AEAEEA71]:0)
	at org.apache.lucene.core@10.0.0-SNAPSHOT/org.apache.lucene.util.packed.Packed64.get(Packed64.java:81)
	at org.apache.lucene.core@10.0.0-SNAPSHOT/org.apache.lucene.index.OrdinalMap$2.get(OrdinalMap.java:346)
	at org.apache.lucene.facet.StringValueFacetCounts.countOneSegment(StringValueFacetCounts.java:440)
	at org.apache.lucene.facet.StringValueFacetCounts.count(StringValueFacetCounts.java:295)
	at org.apache.lucene.facet.StringValueFacetCounts.<init>(StringValueFacetCounts.java:123)
	at org.apache.lucene.facet.TestStringValueFacetCounts.checkFacetResult(TestStringValueFacetCounts.java:349)
	at org.apache.lucene.facet.TestStringValueFacetCounts.testRandom(TestStringValueFacetCounts.java:325)

This looks like a real bug, as StringValueFacetCounts#countOneSegment is called once providing the index of the current loop instead of the ordinal taken from the matching hits that we are analyzing. That works fine with single threaded collection as we will go sequentially and the two indices will always be the same. With multi-threaded search, the order of the returned matching hits (one per segment) is not deterministic.

Issue Links

• links to: GitHub Pull Request #788