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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill issue #594: DRILL-4842: SELECT * on JSON data results in NumberFormatE...
Date Sun, 19 Feb 2017 00:58:16 GMT
Github user paul-rogers commented on the issue:

    https://github.com/apache/drill/pull/594
  
    Note that Drill *does* have a vector that can possibly used to represent a run of nulls:
the {{ZeroVector}}. Using this, we can:
    
    * On the first record where we see a field, if that field is null, add a {{ZeroVector}}
to the record batch.
    * On subsequent records, if the value is still null, do nothing.
    * If the value is non-null, and the current vector is a {{ZeroVector}}, replace it with
the proper Nullable vector, with all (0..i-1) values set to null, and the ith value set to
the current column.
    * At end of batch, if any {{ZeroVector}}s remain, simply remove them so that the column
does not appear in the batch output.
    
    The result of this is that we need not do two map lookups for a null value, we just do
one: the one to find the column value vector as we'd do for an int or string.


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