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https://issues.apache.org/jira/browse/JENA-555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13792708#comment-13792708
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Andy Seaborne commented on JENA-555:
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TDB initialization ({{TDB.wireIntoExecution}}) does this:
{noformat}
StageGenerator orig = (StageGenerator)ARQ.getContext().get(ARQ.stageGenerator) ;
StageGenerator stageGenerator = new StageGeneratorDirectTDB(orig) ;
StageBuilder.setGenerator(ARQ.getContext(), stageGenerator) ;
QC.setFactory(ARQ.getContext(), OpExecutorTDB.OpExecFactoryTDB) ;
{noformat}
which seems to be adding execution for separate graphs in two different ways.
Is this necessary?
> Deprecate StageGenerators prior to removal.
> -------------------------------------------
>
> Key: JENA-555
> URL: https://issues.apache.org/jira/browse/JENA-555
> Project: Apache Jena
> Issue Type: Improvement
> Reporter: Andy Seaborne
> Assignee: Andy Seaborne
>
> StageGenerators are an old way of extending SPARQL query execution. It is
> better to extend OpExecutor (the general purpose algebra execution engine).
> OpExecutor calls the generic StageGenerator currently.
> # Remove StageGenerator from documentation on extending ARQ.
> # Extract the BGP execution into a library.
> # OpExecutor to directly call this library unless the context option is set.
> # Don't set the global context(key = ARQ.stageGenerator) with a
> StageGenerator.
> # Mark StageGenerator \@Deprecated
> # Update examples
> # Check TDB and SDB, esp TDB on single graphs.
> Important here is how a graph from one of those storage subsystems, when
> places in general purpose dataset with other graph types, still manages to go
> to the storage specific BGP execution. (Maybe this does not matter - if it
> misses it will fall back to using {{find()}} so always be correct.)
> We may been to retain the idea of a StageGenerator to catch the single-graph
> case but at least remove as a general extension point in favour of OpExecutor.
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