chsgray opened a new issue, #15351:
URL: https://github.com/apache/datafusion/issues/15351
### Describe the bug
Using the `delta-rs` Python binding, a `DeltaError` was raised when
attempting a `DeltaTable.merge` operation. Library-assigned map field names
appear to be mutually incompatible, which is beyond the user's control.
The error looks like this:
`DeltaError: Generic DeltaTable error: type_coercion
caused by
Error during planning: Failed to coerce then ([Map(Field { name: "entries",
data_type: Struct([Field { name: "key", data_type: Utf8, nullable: false,
dict_id: 0, dict_is_ordered: false, metadata: {} }, Field { name: "value",
data_type: Float64, nullable: true, dict_id: 0, dict_is_ordered: false,
metadata: {} }]), nullable: false, dict_id: 0, dict_is_ordered: false,
metadata: {} }, false), Map(Field { name: "entries", data_type: Struct([Field {
name: "key", data_type: Utf8, nullable: false, dict_id: 0, dict_is_ordered:
false, metadata: {} }, Field { name: "value", data_type: Float64, nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: false,
dict_id: 0, dict_is_ordered: false, metadata: {} }, false), Map(Field { name:
"key_value", data_type: Struct([Field { name: "key", data_type: Utf8, nullable:
false, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field { name:
"value", data_type: Float64, nullable: true, dict_id: 0, dict_is_ordered:
false, metada
ta: {} }]), nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {}
}, false), Map(Field { name: "key_value", data_type: Struct([Field { name:
"key", data_type: Utf8, nullable: false, dict_id: 0, dict_is_ordered: false,
metadata: {} }, Field { name: "value", data_type: Float64, nullable: true,
dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: false, dict_id:
0, dict_is_ordered: false, metadata: {} }, false), Map(Field { name:
"key_value", data_type: Struct([Field { name: "key", data_type: Utf8, nullable:
false, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field { name:
"value", data_type: Float64, nullable: true, dict_id: 0, dict_is_ordered:
false, metadata: {} }]), nullable: false, dict_id: 0, dict_is_ordered: false,
metadata: {} }, false)]) and else (None) to common types in CASE WHEN
expression`
See linked `delta-rs` bug report below for full traceback.
### To Reproduce
Environment
- Python 3.11 on Ubuntu
- Datafusion version:
[45](https://github.com/delta-io/delta-rs/blob/python-v0.25.4/Cargo.toml)
- Delta-rs version: 0.25.4
- Pandas version: 2.2.3
- Pyarrow version: 18.1.0
Python code
```python
import pyarrow as pa
import pandas as pd
import deltalake
path = "~/tmp/test"
schema = pa.schema(
[
pa.field(
"foo",
pa.int64(),
nullable=False,
),
pa.field(
"bar",
pa.map_(pa.string(), pa.float64()),
nullable=True,
),
]
)
df = pd.DataFrame(data={"foo": 1, "bar": [{"baz": 123.4}]})
deltalake.write_deltalake(
path,
pa.Table.from_pandas(df, schema),
mode="append"
)
(
deltalake.DeltaTable(path)
.merge(
pa.Table.from_pandas(df, schema),
predicate="s.foo = t.foo",
target_alias="t",
source_alias="s",
)
.when_matched_update_all()
.when_not_matched_insert_all()
.execute()
)
```
### Expected behavior
I expected the `merge` operation to succeed.
### Additional context
`delta-rs` maintainers indicated this issue is upstream of their library,
which is why I'm raising this here.
The issue I raised there:
[link](https://github.com/delta-io/delta-rs/issues/3340)
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