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From "Andy Seaborne (Commented) (JIRA)" <>
Subject [jira] [Commented] (JENA-178) SPARQL Results serialization is slow for some formats with large result sets
Date Fri, 23 Dec 2011 15:54:30 GMT


Andy Seaborne commented on JENA-178:

The patch looks good.  I vote it gets applied.  Neither of my points below affect that.

IndentedWriter ought to default to no line-based flushing.

I wonder if it ought to have a "setAutoFlush(boolean)" with the default being no flush on
end of line.

I'm unpleasantly surprised that CharsetEncoder pool didn't help.  I wonder if there is a bug
and the pool is, in fact, empty so that a new encoder is created too often.

> SPARQL Results serialization is slow for some formats with large result sets
> ----------------------------------------------------------------------------
>                 Key: JENA-178
>                 URL:
>             Project: Jena
>          Issue Type: Bug
>          Components: ARQ
>    Affects Versions: ARQ 2.8.9
>         Environment: Windows 7 Enterprise 64 bit
>            Reporter: Rob Vesse
>         Attachments:, Jena178.patch,,,
> 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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