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From kkhatua <...@git.apache.org>
Subject [GitHub] drill issue #858: DRILL-3640: Support JDBC Statement.setQueryTimeout(int)
Date Fri, 30 Jun 2017 20:34:20 GMT
Github user kkhatua commented on the issue:

    https://github.com/apache/drill/pull/858
  
    Wouldn't a query cancellation automatically interrupt those potentially blocking operations?
I'm simply looking up whether the trigger was a timeout DrillStatement.isTimedOut() to decide
if the returning exception is a SqlTimeoutExcp.
    
    The extra thread (though mostly sleeping) didn't seem like a huge cost considering that
the timeout is at the granularity of seconds.
    
    I ran a small custom JDBC client application to test this theory. Running longevity and
concurrency testing worked well when testing for timeouts. For timeouts as low as 1 second
for queries that needed to do lot of back end processing before returning rows much later
(like a massive join), I noticed that we caught underlying exceptions as the timeouts during
the 'executeQuery' call itself. If I were to not go the route of issuing a Statement.cancel()
but relying primarily on the DrillCursor, unless I put in some mechanism of constantly polling
for the out-of-time state of the clock. I think then I also need to cancel then cancel all
operations from the level of the DrillCursor in both directions (up to the Statement and down
to the fragments). All this versus issuing a Statement.cancel() that effectively cancels all
the operations down to the fragment level. 
    
    I am now wondering whether I missied a corner case which will be addressed by doing the
timeout in the DrillCursor?


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