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From "Paolo Castagna (Resolved) (JIRA)" <>
Subject [jira] [Resolved] (JENA-117) A pure Java version of tdbloader2, a.k.a. tdbloader3
Date Fri, 09 Mar 2012 12:02:57 GMT


Paolo Castagna resolved JENA-117.

       Resolution: Fixed
    Fix Version/s: TDB 0.9.1
> A pure Java version of tdbloader2, a.k.a. tdbloader3
> ----------------------------------------------------
>                 Key: JENA-117
>                 URL:
>             Project: Apache Jena
>          Issue Type: Improvement
>          Components: TDB
>            Reporter: Paolo Castagna
>            Assignee: Paolo Castagna
>            Priority: Minor
>              Labels: performance, tdbloader2
>             Fix For: TDB 0.9.1
>         Attachments: TDB_JENA-117_r1171714.patch
> There is probably a significant performance improvement for tdbloader2 in replacing the
UNIX sort over text files with an external sorting pure Java implementation.
> Since JENA-99 we now have a SortedDataBag which does exactly that.
>     ThresholdPolicyCount<Tuple<Long>> policy = new ThresholdPolicyCount<Tuple<Long>>(1000000);
>     SerializationFactory<Tuple<Long>> serializerFactory = new TupleSerializationFactory();
>     Comparator<Tuple<Long>> comparator = new TupleComparator();
>     SortedDataBag<Tuple<Long>> sortedDataBag = new SortedDataBag<Tuple<Long>>(policy,
serializerFactory, comparator);
> TupleSerializationFactory greates TupleInputStream|TupleOutputStream which are wrappers
around DataInputStream|DataOutputStream. TupleComparator is trivial.
> Preliminary results seems promising and show that the Java implementation can be faster
than UNIX sort since it uses smaller binary files (instead of text files) and it does comparisons
of long values rather than strings.
> An example of ExternalSort which compare SortedDataBag vs. UNIX sort is available here:
> A further advantage in doing the sorting with Java rather than UNIX sort is that we could
stream results directly into the BPlusTreeRewriter rather than on disk and then reading them
from disk into the BPlusTreeRewriter.
> I've not done an experiment yet to see if this is actually a significant improvement.
> Using compression for intermediate files might help, but more experiments are necessary
to establish if it is worthwhile or not.

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