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  1. Blazegraph (by SYSTAP)
  2. BLZG-404

Deadlines do not play well with GROUP_BY, ORDER_BY, etc.

    Details

    • Type: New Feature
    • Status: Done
    • Resolution: Done
    • Affects Version/s: QUADS_QUERY_BRANCH
    • Fix Version/s: None
    • Component/s: Query Engine

      Description

      Query deadlines do not play well with operators such as GROUP_BY or ORDER_BY which must buffer their outputs. Query deadlines currently interrupt the query, which terminates query processing abruptly. However, operators such as GROUP_BY or ORDER_BY buffer their outputs and may not have written any data when the query deadline elapses.

      One way to handle this is to use a subquery with a deadline to materialize the solutions which are then fed into the parent query where ORDER_BY or GROUP_BY solution modifiers are applied. In addition, the query deadline would have to cause "normal" termination, rather than throwing out a TimeoutException, since exceptions are propagated to the parent query.

      Currently, the deadline is tested each time an operator evaluation task starts or halts. If we introduce long-running tasks, then it might also be worthwhile to add a ScheduledTask to terminate the query after the deadline has expired.

        Activity

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        bryanthompson bryanthompson added a comment -

        This was resolved under a different ticket.

        See BLZG-857 (Query timeout only checked at operator start/stop)
        See BLZG-942 (OutOfMemoryError instead of Timeout for SPARQL Property Paths)

        Show
        bryanthompson bryanthompson added a comment - This was resolved under a different ticket. See BLZG-857 (Query timeout only checked at operator start/stop) See BLZG-942 (OutOfMemoryError instead of Timeout for SPARQL Property Paths)

          People

          • Assignee:
            Unassigned
            Reporter:
            bryanthompson bryanthompson
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            Dates

            • Created:
              Updated:
              Resolved: