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From joshelser <...@git.apache.org>
Subject [GitHub] accumulo pull request #260: ACCUMULO-4643 initial implementation
Date Tue, 30 May 2017 14:47:20 GMT
Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/260#discussion_r119115828
  
    --- Diff: server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java
---
    @@ -586,6 +589,10 @@ private LookupResult lookup(SortedKeyValueIterator<Key,Value>
mmfi, List<Range>
               mmfi.next();
             }
     
    +      } catch (ScanYieldException sye) {
    +        log.debug("Scan yield exception detected at position " + sye.getPosition());
    +        addUnfinishedRange(lookupResult, range, sye.getPosition(), false);
    --- End diff --
    
    What happens to data which is buffered to be sent back to the client, but has not yet
been sent? (the buffer controlled by the tserver scan max memory property). I think the client
would see this data, but I wanted to dbl check with you as you're more familiar than I am
now :)
    
    Specifically, say we have a buffer which can hold 500 Key-Values. An Iterator gets through
250 K-V's, and then throws this exception. We mark the `Range` as unfinished, but does the
client see those 250 K-V's that were produced by the Iterator?
    
    It seems like `addUnfinishedRange(..)` is then determining for us if we need to do any
more work on the current range (e.g. handling the case where we "timed out" after computing
the last k-v for the Range).


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