timsaucer opened a new issue, #715:
URL: https://github.com/apache/datafusion-python/issues/715
**Describe the bug**
When you have a column that is a struct of struct and you attempt to index
into the lowest level, if there is a null at the first level of the struct you
get an unexpected result. In the dataframe below I have an `outer_1` stuct that
if it is null and we try to access an inner member, we would expect to also get
a null.
I have exported this dataframe to parquet and tested on the rust side and
the problem does not exist there, so I think it is something in this repo.
**To Reproduce**
```
ctx = SessionContext()
batch = pa.RecordBatch.from_arrays(
[pa.array([
{"outer_1": {"inner_1": 1, "inner_2": 2}},
{"outer_1": {"inner_1": 1, "inner_2": None}},
{"outer_1": None},
])],
names=["a"],
)
df = ctx.create_dataframe([[batch]])
df.write_parquet("/dbfs/tmp/tsaucer/struct_of_struct.parquet")
df.select(col("a")).show()
df.select(col("a")["outer_1"]).show()
df.select(col("a")["outer_1"]["inner_2"]).show()
```
Produces:
```
03:20 PM (<1s)
ctx = SessionContext()
batch = pa.RecordBatch.from_arrays(
[pa.array([
{"outer_1": {"inner_1": 1, "inner_2": 2}},
{"outer_1": {"inner_1": 1, "inner_2": None}},
{"outer_1": None},
])],
names=["a"],
)
df = ctx.create_dataframe([[batch]])
df.write_parquet("/dbfs/tmp/tsaucer/struct_of_struct.parquet")
df.select(col("a")).show()
df.select(col("a")["outer_1"]).show()
df.select(col("a")["outer_1"]["inner_2"]).show()
DataFrame()
+-------------------------------------+
| a |
+-------------------------------------+
| {outer_1: {inner_1: 1, inner_2: 2}} |
| {outer_1: {inner_1: 1, inner_2: }} |
| {outer_1: } |
+-------------------------------------+
DataFrame()
+----------------------------------------------+
| cc251bd408f114ca2a4354b6976d91339.a[outer_1] |
+----------------------------------------------+
| {inner_1: 1, inner_2: 2} |
| {inner_1: 1, inner_2: } |
| |
+----------------------------------------------+
DataFrame()
+-------------------------------------------------------+
| cc251bd408f114ca2a4354b6976d91339.a[outer_1][inner_2] |
+-------------------------------------------------------+
| 2 |
| |
| 0 |
+-------------------------------------------------------+
```
**Expected behavior**
Accessing a subfield of a null entry should also return null.
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