[JENA-555] Deprecate StageGenerators prior to removal.

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 04/Oct/13 15:31
• Updated: 13/Apr/18 14:30
• Resolved: 13/Apr/18 14:30

Description

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.

1. Remove StageGenerator from documentation on extending ARQ.
2. Extract the BGP execution into a library.
3. OpExecutor to directly call this library unless the context option is set.
4. Don't set the global context(key = ARQ.stageGenerator) with a StageGenerator.
5. Mark StageGenerator @Deprecated
6. Update examples
7. 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.