[OAK-7078] NullPointerException in FilteredSortedSetDocValuesFacetCounts during query evaluation

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.6.7
• Fix Version/s: 1.4.19, 1.6.8, 1.8.0
• Component/s: lucene
• Labels: facet
• Assignee: Vikas Saurabh
• Reporter: Dirk Rudolph
• Created: 18/Dec/17 22:38
• Updated: 10/Jan/18 10:34
• Resolved: 22/Dec/17 16:39

Description

Running the following query select [rep:facet(simple/tags)] from [nt:base] where contains([text], 'ipsum') with the following content

/content/foo
 - text = "lorem lorem"
 + simple/
   - tags = ["tag1", "tag2"]
/content/bar
 - text = "lorem ipsum"

runs in the following NPE

java.lang.NullPointerException
	at org.apache.jackrabbit.oak.plugins.index.lucene.util.FilteredSortedSetDocValuesFacetCounts.getTopChildren(FilteredSortedSetDocValuesFacetCounts.java:63)
	at org.apache.lucene.facet.MultiFacets.getTopChildren(MultiFacets.java:52)
	at org.apache.jackrabbit.oak.plugins.index.lucene.LucenePropertyIndex$LucenePathCursor$2.getValue(LucenePropertyIndex.java:1646)
	... 38 more

This is because the result set for the query only contains /content/bar and with that the count of the dimension simple/tag is 0. For that case SortedSetDocValuesFacetCounts#getDim() returns null and so does getTopChildren.

This expected behaviour is properly handled in LucenePropertyIndex.java#L1647 but not in FilteredSortedSetDocValuesFacetCounts.java#L63 where topChildren is dereferenced without null check.

To workaround that secure facets can be set to false, though the default value is true.