alamb commented on code in PR #7481:
URL: https://github.com/apache/arrow-rs/pull/7481#discussion_r2080096874
##########
parquet/src/arrow/arrow_reader/mod.rs:
##########
@@ -506,37 +525,47 @@ impl ArrowReaderMetadata {
// parquet_to_arrow_field_levels is expected to throw an error if the
schemas have
// different lengths, but we check here to be safe.
if inferred_len != supplied_len {
- Err(arrow_err!(format!(
- "incompatible arrow schema, expected {} columns received {}",
+ return Err(arrow_err!(format!(
+ "Incompatible supplied Arrow schema: expected {} columns
received {}",
inferred_len, supplied_len
- )))
- } else {
- let diff_fields: Vec<_> = supplied_schema
- .fields()
- .iter()
- .zip(fields.iter())
- .filter_map(|(field1, field2)| {
- if field1 != field2 {
- Some(field1.name().clone())
- } else {
- None
- }
- })
- .collect();
+ )));
+ }
- if !diff_fields.is_empty() {
- Err(ParquetError::ArrowError(format!(
- "incompatible arrow schema, the following fields could not
be cast: [{}]",
- diff_fields.join(", ")
- )))
- } else {
- Ok(Self {
- metadata,
- schema: supplied_schema,
- fields: field_levels.levels.map(Arc::new),
- })
+ let mut errors = Vec::new();
Review Comment:
I think relaxing the check means that a user could supply the reader a
schema that had metadata that was not present in the file and the reader will
then read RecordBatches that have that metadata
I agree `field_cast` is the longer term right thing to do in DataFusion
In arrow-rs I think that field "casting" is happening during reading of
parquet
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