SNOW-2213161: explode() with local testing in Snowpark Python fails with AttributeError

[sfc-gh-ksreekandath]

Please answer these questions before submitting your issue. Thanks!

1. What version of Python are you using?

   Python 3.11.0 (main, Jun 30 2025, 10:43:55) [Clang 17.0.0 (clang-1700.0.13.5)]

2. What are the Snowpark Python and pandas versions in the environment?

pandas==2.3.1
snowflake-snowpark-python==1.34.0

3. What did you do?

When attempting to use explode() function in local testing, the below error is seen.

AttributeError: 'MockSelectStatement' object has no attribute 'snowflake_plan'

Here's a step by step repro -

>>> from snowflake.snowpark import Session
>>> from snowflake.snowpark.functions import explode
>>> session = Session.builder.config('local_testing', True).create()
>>> data = [
...     {
...         "foo": "bar",
...         "my_array": ["one","two"]
...     }
... ]
>>> df = session.create_dataframe(data, schema=["foo", "my_array"])
>>> df.show()
--------------------------
|"FOO"  |"MY_ARRAY"      |
--------------------------
|bar    |['one', 'two']  |
--------------------------

>>> df.select("foo", explode("my_array")).show()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/ksreekandath/.pyenv/versions/case_01077035/lib/python3.11/site-packages/snowflake/snowpark/_internal/telemetry.py", line 368, in wrap
    r = func(*args, **kwargs)
        ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ksreekandath/.pyenv/versions/case_01077035/lib/python3.11/site-packages/snowflake/snowpark/_internal/utils.py", line 1120, in call_wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ksreekandath/.pyenv/versions/case_01077035/lib/python3.11/site-packages/snowflake/snowpark/dataframe.py", line 1634, in select
    new_cols, alias_cols = _get_cols_after_explode_join(
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/ksreekandath/.pyenv/versions/case_01077035/lib/python3.11/site-packages/snowflake/snowpark/table_function.py", line 327, in _get_cols_after_explode_join
    plan = select_statement.select([func.col._named()]).snowflake_plan
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'MockSelectStatement' object has no attribute 'snowflake_plan'
>>> 

4. What did you expect to see?

>>> from snowflake.snowpark import Session
from snowflake.snowpark.functions import explode
>>> session=Session.builder.config("connection_name","XTB17692").create()
>>> data = [
...     {
...         "foo": "bar",
...         "my_array": ["one","two"]
...     }
... ]
>>> df = session.create_dataframe(data, schema=["foo", "my_array"])
>>> df.show()
----------------------
|"FOO"  |"MY_ARRAY"  |
----------------------
|bar    |[           |
|       |  "one",    |
|       |  "two"     |
|       |]           |
----------------------

>>> df.select("foo", explode("my_array")).show()
-------------------
|"FOO"  |"VALUE"  |
-------------------
|bar    |"one"    |
|bar    |"two"    |
-------------------

>>> 
>>> 

[sfc-gh-sghosh]

Hello @sfc-gh-ksreekandath ,

Thanks for raising the issue, we have been able to reproduce the issue, we will work on eliminating it.

Regards,
Sujan

[JoshElkind]

Hi @sfc-gh-jrose ,

I've submitted a fix for this issue in PR #4085.

Root cause: Two gaps in the local testing mock framework:

MockSelectStatement was missing the snowflake_plan property that table_function.py uses for schema inference

The mock execution engine had no implementation for the built-in FLATTEN table function (which explode() uses internally)

The fix:

Added snowflake_plan property to MockSelectable for API compatibility
Implemented handle_flatten_function() to execute FLATTEN locally for arrays and objects

Supports explode(), explode_outer(), and flatten() with input, outer, and mode parameters