[Bigdata-developers] SPARQL UPDATE performance fix

[Bryan T. <br...@sy...>]

We found a bug in the openrdf library that is having a very strong negative
impact on SPARQL UPDATE performance for larger UPDATE sets.  The root cause
is MultipleTupleQueryResult using LinkedList.get(index), which is a linear
scan, for next().  So the iterator performance falls off linearly as the
scan progresses.

For the impatient, there is a very simple fix:

1. Clone the MutableTupleQueryResult class in openrdf into a new namespace
in blazegraph.
2. Replace LinkedList with ArrayList (one line change);
3. Import that modified version of the class in our AST2BOpUpdate class
(one line change).

Michael is testing the performance impact of that fix now.

See https://jira.blazegraph.com/browse/BLZG-1404

Thanks,
Bryan