[jira] [Created] (SPARK-18859) Catalyst codegen does not mark column as nullable when it should. Causes NPE

["Mykhailo Osypov (JIRA)" <ji...@apache.org>]

Mykhailo Osypov created SPARK-18859:
---------------------------------------

             Summary: Catalyst codegen does not mark column as nullable when it should. Causes NPE
                 Key: SPARK-18859
                 URL: https://issues.apache.org/jira/browse/SPARK-18859
             Project: Spark
          Issue Type: Bug
          Components: Optimizer, SQL
    Affects Versions: 2.0.2
            Reporter: Mykhailo Osypov
            Priority: Critical


When joining two tables via LEFT JOIN, columns in right table may be NULLs, however catalyst codegen cannot recognize it.
Example:
```
create table masterdata.testtable(
  id int not null,
  age int
);
create table masterdata.jointable(
  id int not null,
  name text not null
);

(select t.id, t.age, j.name from masterdata.testtable t left join masterdata.jointable j on t.id = j.id) as testtable;
```
```
val df = sqlContext
      .read
      .format("jdbc")
      ..option("dbTable", "query to select)
     ....
      .load
//df generated schema
/*
root
 |-- id: integer (nullable = false)
 |-- age: integer (nullable = true)
 |-- name: string (nullable = false)
*/
```
CODEGEN
```
/* 038 */       scan_rowWriter.write(0, scan_value);
/* 039 */
/* 040 */       if (scan_isNull1) {
/* 041 */         scan_rowWriter.setNullAt(1);
/* 042 */       } else {
/* 043 */         scan_rowWriter.write(1, scan_value1);
/* 044 */       }
/* 045 */
/* 046 */       scan_rowWriter.write(2, scan_value2);
```

Since j.name is from right table of left join query, it may be null. However generated schema doesn't think so (probably because it defined as name text not null)



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