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https://issues.apache.org/jira/browse/JENA-2302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17502941#comment-17502941
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Andy Seaborne commented on JENA-2302:
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A quick glance and it looks good.
It needs to cope with the results-then-head case, not necessarily be as
performant. If that situation occurs in the wild, I would expect it i more
likely with small results rather that large. It is possible to determine the
variables from the query itself, there is no need to scan the results.
# Is results-then-head tested? It probably isn't in the ARQ test suite (please
add!)
# I don't see ASK results covered. Maybe I missed that.
# Do you have performance measurements?
# Formally {{DataBag}} is not order preserving (IIRC).
# When does it spill? Or even in-memory only for the delayed results.
# Please use constants for keyworks : {{JSONResultsKW}}
# I didn't see coverage of the legacy case {{kTypedLiteral}} "typed-literal"
# No author tags please.
GSON:
# How big is GSON (with dependencies, i.e. impact on Fuseki)?
# Is the proposed code only using the parser with no data mapping? (This is
the risk for injection attacks that Jackson went through).
Two things next:
* PR
* Could you please email users@ to say the work is in-progress? See if we can
identify any corner cases.
The JSON results are quite important so we have to take care that a release is
not going to cause problems.
> RowSetReaderJSON is not streaming
> ---------------------------------
>
> Key: JENA-2302
> URL: https://issues.apache.org/jira/browse/JENA-2302
> Project: Apache Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: Jena 4.5.0
> Reporter: Claus Stadler
> Priority: Major
>
> Retrieving all data from our TDB2 endpoint with jena 4.5.0-SNAPSHOT is no
> longer streaming for the JSON format. I tracked the issue to RowSetReaderJson
> which reads everything into in memory (and then checks whether it is a SPARQL
> ASK result)
> {code:java}
> public class RowSetReaderJson {
> private void parse(InputStream in) {
> JsonObject obj = JSON.parse(in); // !!! Loads everything !!!
> // Boolean?
> if ( obj.hasKey(kBoolean) ) { ... }
> }
> }
> {code}
> Streaming works when switching the to RS_XML in the example below:
> {code:java}
> public class Main {
> public static void main(String[] args) {
> System.out.println("Test Started");
> try (QueryExecution qe = QueryExecutionHTTP.create()
>
> .acceptHeader(ResultSetLang.RS_JSON.getContentType().getContentTypeStr())
> .endpoint("http://moin.aksw.org/sparql";).queryString("SELECT
> * { ?s ?p ?o }").build()) {
> qe.execSelect().forEachRemaining(System.out::println);
> }
> System.out.println("Done");
> }
> }
> {code}
> For completeness, I can rule out any problem with TDB2 because streaming of
> JSON works just fine with:
> {code:bash}
> curl --data-urlencode "query=select * { ?s ?p ?o }"
> "http://moin.aksw.org/sparql";
> {code}
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