On 5th March 2014 we received alerts about a search server index failure during recording indexing. We're running the latest version of the search server:

recording:Indexing 13720000...13739999 / 15913247 (86%)
Exception in thread "main" java.lang.NullPointerException
at org.musicbrainz.search.index.ArtistCreditHelper.updateArtistCreditWithAliases(ArtistCreditHelper.java:156)
at org.musicbrainz.search.index.RecordingIndex.updateTrackArtistCreditWithAliases(RecordingIndex.java:399)
at org.musicbrainz.search.index.RecordingIndex.indexData(RecordingIndex.java:747)
at org.musicbrainz.search.index.IndexBuilder.buildDatabaseIndex(IndexBuilder.java:271)
at org.musicbrainz.search.index.IndexBuilder.main(IndexBuilder.java:160)

Looks like the offending line expects these chained function calls to never return null:

nc = acw.getArtistCredit().getNameCredit().get(currPosition);

Given it's be running fine and we've made no alterations to our production system since the last schema update, I'm guessing that this is a data driven issue.