Cheng Lian created SPARK-1959:
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Summary: String "NULL" is interpreted as null value
Key: SPARK-1959
URL: https://issues.apache.org/jira/browse/SPARK-1959
Project: Spark
Issue Type: Bug
Components: SQL
Affects Versions: 1.0.0
Reporter: Cheng Lian
The {{HiveTableScan}} operator unwraps string "NULL" (case insensitive) into
null values even if the column type is {{STRING}}.
To reproduce the bug, we use
{{sql/hive/src/test/resources/groupby_groupingid.txt}} as test input, copied to
{{/tmp/groupby_groupingid.txt}}.
Hive session:
{code}
hive> CREATE TABLE test_null(key INT, value STRING);
hive> LOAD DATA LOCAL INPATH '/tmp/groupby_groupingid.txt' INTO table test_null;
hive> SELECT * FROM test_null WHERE value IS NOT NULL;
...
OK
1 NULL
1 1
2 2
3 3
3 NULL
4 5
1 NULL
1 1
2 2
3 3
3 NULL
4 5
{code}
We can see that the {{NULL}} cells in the original input file are interpreted
as string {{"NULL"}} in Hive.
Spark SQL session ({{sbt/sbt hive/console}}):
{code}
scala> hql("CREATE TABLE test_null(key INT, value STRING)")
scala> hql("LOAD DATA LOCAL INPATH '/tmp/groupby_groupingid.txt' INTO table
test_null")
scala> hql("SELECT * FROM test_null WHERE value IS NOT NULL").foreach(println)
...
[1,1]
[2,2]
[3,3]
[4,5]
{code}
As we can see, string {{"NULL"}} is interpreted as null values in Spark SQL.
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