[GitHub] drill issue #860: DRILL-5601: Rollup of external sort fixes and improvements

[paul-rogers <gi...@git.apache.org>]

Github user paul-rogers commented on the issue:

    https://github.com/apache/drill/pull/860
  
    # Additional Revisions
    
    The code contains an optimization for short queries. If the query has just one batch then the sort need not copy that batch to produce the output. Instead, the sort simply passes along the input batch along with an SV2. This commit fixes some issues with transferring that single, buffered, input batch to the sort’s output container.
    
    While reproducing problems found by QA, it turned out to be useful to be able to parse SQL statements from a file in the context of the test framework. Added test methods for this purpose.
    
    The “AllocationHelper” class turns out to throw an exception if asked to allocate a vector with zero elements. Since a zero-size can occasionally come from the record batch sizer (via the “smart allocation helper”, special code was added to handle this case.
    
    Backed out some debugging code that accidentally appeared in the original PR.
    
    With this set of improvements, the revised, managed sort has become more stable and reliable than the original version. As a result, this commit enables the managed sort by default.


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