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From "David Maughan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-15328) Inconsistent/incorrect handling of NULL in nested structs
Date Thu, 01 Dec 2016 12:56:58 GMT
David Maughan created HIVE-15328:
------------------------------------

             Summary: Inconsistent/incorrect handling of NULL in nested structs
                 Key: HIVE-15328
                 URL: https://issues.apache.org/jira/browse/HIVE-15328
             Project: Hive
          Issue Type: Bug
          Components: Hive
    Affects Versions: 2.1.0
            Reporter: David Maughan


h2. Overview

Performing {{IS NULL}} checks against a null struct that is generated as part of a UDF correctly
returns {{true}}. However, the same check against the same null struct that has been persisted
to a table incorrectly returns {{false}}. Additionally, when a child field of the null struct
is inspected in the same query, the result of the null check on the struct itself reverses
itself to {{true}}.

The issue does not appear to be dependent on the storage format of the table as the same result
is repeated with TEXTFILE, PARQUET, ORC and AVRO.

h2. Example

In this example I have used {{if(1=1, null, named_struct('c', 1)}} as a crude method of generating
a simple null struct.

h4. 'b' is correctly reported as {{true}}.
{code}
hive> select
    >   b is null,
    >   b
    > from (
    >   select
    >     if(1=1, null, named_struct('c', 1)) as b
    >   ) as a;
OK
true	NULL
{code}

h4. 'b' is correctly reported as {{true}} when also inspecting 'b.c'.
{code}
hive>
    > select
    >   b is null,
    >   b.c is null,
    >   b
    > from (
    >   select
    >     if(1=1, null, named_struct('c', 1)) as b
    >   ) as a;
OK
true	true	NULL
{code}

h4. Persist the data to a table
{code}
hive>
    > create table a
    >   as
    > select
    >   if(1=1, null, named_struct('c', 1)) as b;
OK
{code}

h4. 'b' is incorrectly reported as {{false}}.
{code}
hive>
    > select
    >   b is null,
    >   b
    > from a;
OK
false	NULL
{code}

h4. 'b' is now correctly reported as {{true}} when also inspecting 'b.c'.
{code}
hive>
    > select
    >   b is null,
    >   b.c is null,
    >   b
    > from a;
OK
true	true	NULL
{code}



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