[GitHub] [jena] afs commented on issue #1557: Make projected dataset in DynamicDataset accessible

[GitBox <gi...@apache.org>]

afs commented on issue #1557:
URL: https://github.com/apache/jena/issues/1557#issuecomment-1264392984

   Outstanding questions:
   * Is the data in TDB? Or externally stored data?
   * What is the actual slow part?
   
   There are two potential costs in `GraphUnionRead`:
   * it works in nodes when 2+ graphs
   * it does general distinct that materialised nodes
   
   When all the graphs are in a single TDB (either TDB1 or TDB2):
   
   ```SELECT (COUNT(*) AS ?c) FROM <x> FROM <y> { ?s ?p ?o }```
   
   can be addressed by pushing down the work into TDB and not using the general purpose `GraphUnionRead`. It will get the right answers. This isn't easy - something will need to change because now we might multiple quad filtering in one access. You'll need this anyway later on.
   
   You may wish to review the requirements that Vilnis Termanis. Not the same but related - maybe there is a single solution.
   


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