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  1. Blazegraph (by SYSTAP)
  2. BLZG-1252

Flatten sub-selects for improved join ordering

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    Details

    • Type: New Feature
    • Status: Open
    • Resolution: Unresolved
    • Affects Version/s: BLAZEGRAPH_RELEASE_1_5_1
    • Fix Version/s: None
    • Component/s: Query Plan Generator
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      Description

      Andrey Gubichev suggests that sub-selects with aggregates can be flattened as well, see papers by Galindo-Legaria (e.g., Orthogonal Optimization of Subqueries and Aggregation). In short, group by in the subquery is transferred on top of the outer query, with adding a left outer join between the outer query and the subquery. This provides a path for simplification of complex queries that could support both the runtime query optimizer or optimization based on characteristic sets and characteristic pairs per the work on RDF3x.

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              Assignee:
              michaelschmidt michaelschmidt
              Reporter:
              bryanthompson bryanthompson
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                Created:
                Updated: