[jira] [Created] (SPARK-14040) Null-safe and equality join produces incorrect result with filtered dataframe

["Denton Cockburn (JIRA)" <ji...@apache.org>]

Denton Cockburn created SPARK-14040:
---------------------------------------

             Summary: Null-safe and equality join produces incorrect result with filtered dataframe
                 Key: SPARK-14040
                 URL: https://issues.apache.org/jira/browse/SPARK-14040
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 1.6.0
         Environment: Ubuntu Linux 15.10
            Reporter: Denton Cockburn


Initial issue reported here: http://stackoverflow.com/questions/36131942/spark-join-produces-wrong-results

```
val b = Seq(("a", "b", 1), ("a", "b", 2)).toDF("a", "b", "c")
val a = b.where("c = 1").withColumnRenamed("a", "filta").withColumnRenamed("b", "filtb")

a.join(b, $"filta" <=> $"a" and $"filtb" <=> $"b" and a("c") <=> b("c"), "left_outer").show
```

Produces 2 rows instead of the expected 1.

```
a.withColumn("newc", $"c").join(b, $"filta" === $"a" and $"filtb" === $"b" and $"newc" === b("c"), "left_outer").show
```

Also produces 2 rows instead of the expected 1.

The only one that seemed to work correctly was:
```
a.join(b, $"filta" === $"a" and $"filtb" === $"b" and a("c") === b("c"), "left_outer").show
```

But that produced a warning for : ``` WARN Column: Constructing trivially true equals predicate, 'c#18232 = c#18232' ```

As pointed out by commenter zero323:
"The second behavior looks indeed like a bug related to the fact that you still have a.c in your data. It looks like it is picked downstream before b.c and the evaluated condition is actually a.newc = a.c"



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