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From Zelaine Fong <zf...@maprtech.com>
Subject Re: Query a field with empty list
Date Mon, 02 Nov 2015 19:50:04 GMT
Wouldn't it make more sense to return an empty list in this case?  Null is
not quite the same as an empty list.  So, I would think you'd want a
distinction between the two.

-- Zelaine

On Mon, Nov 2, 2015 at 11:41 AM, Hsuan Yi Chu <hyichu@maprtech.com> wrote:

> There could be inconsistent results:
> https://issues.apache.org/jira/browse/DRILL-4007
>
> On Mon, Nov 2, 2015 at 8:17 AM, Andries Engelbrecht <
> aengelbrecht@maprtech.com> wrote:
>
> > Currently in 1.2 I observe the following.
> >
> > 0: jdbc:drill:> select a from dfs.json.`/test.json`;
> > +-------+
> > |   a   |
> > +-------+
> > | null  |
> > +———+
> >
> > But then flatten produces an error
> >
> > 0: jdbc:drill:> select flatten(a) from dfs.json.`/test.json`;
> > Error: SYSTEM ERROR: ClassCastException: Cannot cast
> > org.apache.drill.exec.vector.NullableIntVector to
> > org.apache.drill.exec.vector.complex.RepeatedValueVector
> >
> > Ideally both should return similar responses, in most cases it may be
> > easier to work with a null being returned than no record or an empty
> > string. Returning [] might be interpreted as a string data type pending
> > user experience or tools being used??
> >
> > —Andries
> >
> >
> >
> > > On Oct 31, 2015, at 4:44 PM, Hsuan Yi Chu <hyichu@maprtech.com> wrote:
> > >
> > > Hi,
> > > For example, say, we are querying a field with empty list:
> > >
> > > select a from `XXX,json`
> > >
> > > {
> > > a: []
> > > }
> > >
> > > What is the expected result in the sqlline? Which one of the following
> > > should it be?
> > >
> > > 1. []
> > > 2. null
> > > 3. no record
> > >
> > > Thanks.
> >
> >
>

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