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[SPARK-19165][PYTHON][SQL] PySpark APIs using columns as arguments should...
[SPARK-19165][PYTHON][SQL] PySpark APIs using columns as arguments should validate input types for column ## What changes were proposed in this pull request? While preparing to take over https://github.com/apache/spark/pull/16537, I realised a (I think) better approach to make the exception handling in one point. This PR proposes to fix `_to_java_column` in `pyspark.sql.column`, which most of functions in `functions.py` and some other APIs use. This `_to_java_column` basically looks not working with other types than `pyspark.sql.column.Column` or string (`str` and `unicode`). If this is not `Column`, then it calls `_create_column_from_name` which calls `functions.col` within JVM: https://github.com/apache/spark/blob/42b9eda80e975d970c3e8da4047b318b83dd269f/sql/core/src/main/scala/org/apache/spark/sql/functions.scala#L76 And it looks we only have `String` one with `col`. So, these should work: ```python >>> from pyspark.sql.column import _to_java_column, Column >>> _to_java_column("a") JavaObject id=o28 >>> _to_java_column(u"a") JavaObject id=o29 >>> _to_java_column(spark.range(1).id) JavaObject id=o33 ``` whereas these do not: ```python >>> _to_java_column(1) ``` ``` ... py4j.protocol.Py4JError: An error occurred while calling z:org.apache.spark.sql.functions.col. Trace: py4j.Py4JException: Method col([class java.lang.Integer]) does not exist ... ``` ```python >>> _to_java_column([]) ``` ``` ... py4j.protocol.Py4JError: An error occurred while calling z:org.apache.spark.sql.functions.col. Trace: py4j.Py4JException: Method col([class java.util.ArrayList]) does not exist ... ``` ```python >>> class A(): pass >>> _to_java_column(A()) ``` ``` ... AttributeError: 'A' object has no attribute '_get_object_id' ``` Meaning most of functions using `_to_java_column` such as `udf` or `to_json` or some other APIs throw an exception as below: ```python >>> from pyspark.sql.functions import udf >>> udf(lambda x: x)(None) ``` ``` ... py4j.protocol.Py4JJavaError: An error occurred while calling z:org.apache.spark.sql.functions.col. : java.lang.NullPointerException ... ``` ```python >>> from pyspark.sql.functions import to_json >>> to_json(None) ``` ``` ... py4j.protocol.Py4JJavaError: An error occurred while calling z:org.apache.spark.sql.functions.col. : java.lang.NullPointerException ... ``` **After this PR**: ```python >>> from pyspark.sql.functions import udf >>> udf(lambda x: x)(None) ... ``` ``` TypeError: Invalid argument, not a string or column: None of type <type 'NoneType'>. For column literals, use 'lit', 'array', 'struct' or 'create_map' functions. ``` ```python >>> from pyspark.sql.functions import to_json >>> to_json(None) ``` ``` ... TypeError: Invalid argument, not a string or column: None of type <type 'NoneType'>. For column literals, use 'lit', 'array', 'struct' or 'create_map' functions. ``` ## How was this patch tested? Unit tests added in `python/pyspark/sql/tests.py` and manual tests. Author: hyukjinkwon <gurwls223@gmail.com> Author: zero323 <zero323@users.noreply.github.com> Closes #19027 from HyukjinKwon/SPARK-19165.
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