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https://issues.apache.org/jira/browse/JENA-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13168873#comment-13168873
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Rob Vesse commented on JENA-178:
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So a couple more notes - for these figures the dataset was LUBM 0 with
materialized forward chained inferences giving approx 138,000 triples loaded
into a TDB database. The performance problem I've seen is not dataset
specific, I've seen similarily bad performance on a variety of datasets when
queries yield large results. The Fuseki instance is running on the local
machine so the HTTP overhead should be minimal.
I looked into the code and I can't seen anything untoward for SPARQL XML at
least, it looks like results are serialized and parsed in a fully streaming
fashion. Certainly serialization all appears to be done with string
manipulation which should in theory at least be fast. I will try and create a
minimal test case that just exercises the parser and the serializer on local
in-memory data and would allow easier profiling to see what may be going wrong.
> SPARQL Results serialization and parsing is slow with large result sets
> -----------------------------------------------------------------------
>
> Key: JENA-178
> URL: https://issues.apache.org/jira/browse/JENA-178
> Project: Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: ARQ 2.8.9
> Environment: Windows 7 Enterprise 64 bit
> Reporter: Rob Vesse
>
> The SPARQL XML and JSON Result formats are very slow when the result set is
> large. This is surprising to me since both formats are relatively simple and
> should lend themselves to fairly fast streaming serialization and parsing.
> The following are observed performance figures comparing SPARQL XML, SPARQL
> JSON and SPARQL TSV results format. This is the averaged time over 5 runs to
> retrieve the first 50,000 triples from the dataset with a simple SELECT *
> WHERE { ?s ?p ?o } LIMIT 50000 via a HTTP request to Fuseki and iterate over
> the results on the client.
> SPARQL XML = 15.25 seconds
> SPARQL JSON = 10.9 seconds
> SPARQL TSV = 0.54 seconds
> Now obviously TSV is way simpler to serialize and parse than XML/JSON but
> these serializers and parsers should not be 20-30 times slower IMO
> Also for comparison note that doing an equivalent CONSTRUCT { ?s ?p ?p }
> WHERE { ?s ?p ?o } LIMIT 50000 takes only about 2s and that is using RDF/XML
> serialization which I would have expected to be slower because RDF/XML is
> more complex to generate than either SPARQL XML/JSON results. I haven't
> dived into the code in detail to investigate why this is slow yet but do the
> Jena team have any thoughts on this?
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