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Merged
phillipleblanc merged 3 commits into from
Dec 5, 2025
Merged

Improve error message and add debug logging for cast failures #63

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235e7ce
Add tracing debug/trace logging on schema cast failures
phillipleblanc Dec 4, 2025
368efd0
better cast error
phillipleblanc Dec 4, 2025
f622758
Add the actual value into the error
phillipleblanc Dec 4, 2025
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2 changes: 1 addition & 1 deletion datafusion-federation/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -26,11 +26,11 @@ async-trait.workspace = true
datafusion.workspace = true
async-stream.workspace = true
arrow-json.workspace = true
tracing = "0.1"

[dev-dependencies]
tokio.workspace = true
tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
tracing = "0.1.40"
insta = { version = "1.42.0", features = ["filters"] }

[[example]]
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2 changes: 1 addition & 1 deletion datafusion-federation/src/schema_cast/lists_cast.rs
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Expand Up @@ -30,7 +30,7 @@ macro_rules! cast_string_to_list_array {
None => list_builder.append_null(),
Some(string_value) => {
decoder.decode(string_value.as_bytes()).map_err(|e| {
ArrowError::CastError(format!("Failed to decode value: {e}"))
ArrowError::CastError(format!("Failed to decode value {string_value}: {e}"))
})?;

if let Some(b) = decoder.flush().map_err(|e| {
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78 changes: 64 additions & 14 deletions datafusion-federation/src/schema_cast/record_convert.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,14 @@ pub enum Error {
source: datafusion::arrow::error::ArrowError,
},

UnableToCastColumn {
source: datafusion::arrow::error::ArrowError,
column_index: usize,
column_name: String,
from_type: DataType,
to_type: DataType,
},

UnexpectedNumberOfColumns {
expected: usize,
found: usize,
Expand All @@ -35,6 +43,18 @@ impl std::fmt::Display for Error {
Error::UnableToConvertRecordBatch { source } => {
write!(f, "Unable to convert record batch: {source}")
}
Error::UnableToCastColumn {
source,
column_index,
column_name,
from_type,
to_type,
} => {
write!(
f,
"Unable to cast column {column_index} '{column_name}' from {from_type} to {to_type}: {source}"
)
}
Error::UnexpectedNumberOfColumns { expected, found } => {
write!(
f,
Expand All @@ -52,6 +72,12 @@ pub fn try_cast_to(record_batch: RecordBatch, expected_schema: SchemaRef) -> Res
let actual_schema = record_batch.schema();

if actual_schema.fields().len() != expected_schema.fields().len() {
tracing::debug!(
actual_schema = ?actual_schema,
expected_schema = ?expected_schema,
"Schema mismatch in try_cast_to"
);
tracing::trace!(record_batch = ?record_batch, "Record batch contents");
return Err(Error::UnexpectedNumberOfColumns {
expected: expected_schema.fields().len(),
found: actual_schema.fields().len(),
Expand All @@ -64,68 +90,92 @@ pub fn try_cast_to(record_batch: RecordBatch, expected_schema: SchemaRef) -> Res
.enumerate()
.map(|(i, expected_field)| {
let record_batch_col = record_batch.column(i);
let from_type = record_batch_col.data_type().clone();
let to_type = expected_field.data_type().clone();
let make_err = |e| Error::UnableToCastColumn {
source: e,
column_index: i,
column_name: expected_field.name().clone(),
from_type: from_type.clone(),
to_type: to_type.clone(),
};

match (record_batch_col.data_type(), expected_field.data_type()) {
(DataType::Utf8, DataType::List(item_type)) => {
cast_string_to_list::<i32>(&Arc::clone(record_batch_col), item_type)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::Utf8, DataType::LargeList(item_type)) => {
cast_string_to_large_list::<i32>(&Arc::clone(record_batch_col), item_type)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::Utf8, DataType::FixedSizeList(item_type, value_length)) => {
cast_string_to_fixed_size_list::<i32>(
&Arc::clone(record_batch_col),
item_type,
*value_length,
)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::Utf8, DataType::Struct(_)) => cast_string_to_struct::<i32>(
&Arc::clone(record_batch_col),
expected_field.clone(),
)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e }),
.map_err(make_err),
(DataType::LargeUtf8, DataType::List(item_type)) => {
cast_string_to_list::<i64>(&Arc::clone(record_batch_col), item_type)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::LargeUtf8, DataType::LargeList(item_type)) => {
cast_string_to_large_list::<i64>(&Arc::clone(record_batch_col), item_type)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::LargeUtf8, DataType::FixedSizeList(item_type, value_length)) => {
cast_string_to_fixed_size_list::<i64>(
&Arc::clone(record_batch_col),
item_type,
*value_length,
)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
.map_err(make_err)
}
(DataType::LargeUtf8, DataType::Struct(_)) => cast_string_to_struct::<i64>(
&Arc::clone(record_batch_col),
expected_field.clone(),
)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e }),
.map_err(make_err),
(
DataType::Interval(IntervalUnit::MonthDayNano),
DataType::Interval(IntervalUnit::YearMonth),
) => cast_interval_monthdaynano_to_yearmonth(&Arc::clone(record_batch_col))
.map_err(|e| Error::UnableToConvertRecordBatch { source: e }),
.map_err(make_err),
(
DataType::Interval(IntervalUnit::MonthDayNano),
DataType::Interval(IntervalUnit::DayTime),
) => cast_interval_monthdaynano_to_daytime(&Arc::clone(record_batch_col))
.map_err(|e| Error::UnableToConvertRecordBatch { source: e }),
.map_err(make_err),
_ => cast(&Arc::clone(record_batch_col), expected_field.data_type())
.map_err(|e| Error::UnableToConvertRecordBatch { source: e }),
.map_err(make_err),
}
})
.collect::<Result<Vec<Arc<dyn Array>>>>()?;
.collect::<Result<Vec<Arc<dyn Array>>>>()
.inspect_err(|_| {
tracing::debug!(
actual_schema = ?actual_schema,
expected_schema = ?expected_schema,
"Cast error in try_cast_to"
);
tracing::trace!(record_batch = ?record_batch, "Record batch contents");
})?;

RecordBatch::try_new(expected_schema, cols)
.map_err(|e| Error::UnableToConvertRecordBatch { source: e })
RecordBatch::try_new(expected_schema.clone(), cols).map_err(|e| {
tracing::debug!(
actual_schema = ?actual_schema,
expected_schema = ?expected_schema,
"RecordBatch creation error in try_cast_to"
);
tracing::trace!(record_batch = ?record_batch, "Record batch contents");
Error::UnableToConvertRecordBatch { source: e }
})
}

#[cfg(test)]
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