Crash with simple ?rel query

[niklas88]

I'm trying to figure this out myself but wanted to document here nonetheless and maybe @Buchhold sees the problem immediately:
Executing the following query on our internal QLever instance crashes with std::bad_alloc, the same query gives normal results on Virtuoso:

PREFIX fb: <http://rdf.freebase.com/ns/>

SELECT DISTINCT ?rel
WHERE {
    fb:m.02hrh1q ?rel fb:m.02rshjk .
}

This is after more than 27000 queries of the same form worked so pretty specific to these entities.
The output running in GDB suggests there is something wrong with the special case in Index::scanNonFunctionalRelation

[niklas88]

It seems this is quite old and hopefully mature code so I'm a bit confused, is there some documentation of the file formats? From what I can see, I'd guess that somehow the follower block's offset is smaller than the lower_bound's offset resulting in an underflow here

[niklas88]

@Buchhold is it possible that we shouldn't read from _psoFile but from indexFile here? It seems to me that _psoFile is a WidthTwoList so pairs of Ids but we're trying to read a pair<Id, off_t> which is what indexFile consists of? Also the comments say we want to read a follow block but blocks are read from the indexFile

[Buchhold]

Thanks a lot. Just had a look, you're obviously right. should be indexFile