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https://issues.apache.org/jira/browse/JENA-1862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17061928#comment-17061928
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Claus Stadler commented on JENA-1862:
-------------------------------------
Hi Andy, I have implemented the described approach and created a test case that
piped all *.rq that were parsable under arq/testing through it
https://github.com/apache/jena/compare/master...Aklakan:JENA-1862#diff-f94bfaf468aaab2ba094bf845abaf4a3R76
The status is, that there are 1234 queries in total, but 6 caused errors and 9
result in deviation from the original clone method - so the vast majority is
working.
On first glance, most deviations are simply due to base IRIs getting expanded
with the current working directory - not sure how much plumbing it would take
to disable it in the current syntax transform code :/
The errors seem to be for queries such as
./jena-arq/testing/DAWG-Final/syntax-sparql2/syntax-form-describe01.rq which
only contains "DESCRIBE <u>"
{code}
java.lang.NullPointerException
at
org.apache.jena.sparql.serializer.FormatterElement.visit(FormatterElement.java:310)
at
org.apache.jena.sparql.syntax.ElementGroup.visit(ElementGroup.java:120)
at
org.apache.jena.sparql.serializer.FormatterElement.visitAsGroup(FormatterElement.java:442)
at
org.apache.jena.sparql.serializer.QuerySerializer.visitQueryPattern(QuerySerializer.java:207)
at org.apache.jena.query.Query.visit(Query.java:756)
at org.apache.jena.query.Query.serialize(Query.java:914)
at org.apache.jena.query.Query.serialize(Query.java:891)
at org.apache.jena.query.Query.serialize(Query.java:881)
at org.apache.jena.query.Query.serialize(Query.java:842)
at org.apache.jena.query.Query.toString(Query.java:787)
{code}
I also already fixed a glitch in my code where named graphs are incorrectly
added as default graphs:
https://github.com/apache/jena/blob/master/jena-arq/src/main/java/org/apache/jena/sparql/syntax/syntaxtransform/QueryTransformOps.java#L169
> Query.cloneQuery is slow
> ------------------------
>
> Key: JENA-1862
> URL: https://issues.apache.org/jira/browse/JENA-1862
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 3.14.0
> Reporter: Claus Stadler
> Priority: Major
>
> This is a follow up to JENA-1861 which is about the thread safety of Query
> objects. As sharing a Query object across threads may introduce race
> conditions, the obvious workaround would be to just clone it. However, the
> current implementation serializes the query to string and then re-parses it
> which causes a very high overhead (for my use case it became the top entry in
> the VisualVM profiler).
> Proposal:
> * Extend ElementTransformCopyBase with a 'alwaysCopy' flag analogous to
> ExprTransformCopy
> * Add a new constructor to
> ExprTransformApplyElementTransform(ElementTransform transform, boolean
> alwaysCopy) so that the alwayCopy flag of the underlying ExprTransformCopy
> can be set to true
> * Implement clone using syntatic transforms as below
> {code:java}
> public static Query fastClone(Query query) {
> ElementTransform eltXform = new ElementTransformCopyBase2(true);
> ExprTransform exprXform = new
> ExprTransformApplyElementTransform2(eltXform, true);
> Query result = QueryTransformOps.transform(query, eltXform, exprXform);
> return result;
> }
> {code}
> This approach 'works-for-me' and I can create a pull request for this, but
> maybe there are more subtleties to the outlined approach that need to be
> considered?
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