comphead commented on code in PR #15840:
URL: https://github.com/apache/datafusion/pull/15840#discussion_r2066843997
##########
datafusion/datasource-avro/src/avro_to_arrow/reader.rs:
##########
@@ -133,19 +133,37 @@ impl<R: Read> Reader<'_, R> {
///
/// If reading a `File`, you can customise the Reader, such as to enable
schema
/// inference, use `ReaderBuilder`.
+ ///
+ /// If projection is provided, it uses a schema with only the fields in
the projection, respecting their order.
+ /// Only the first level of projection is handled. No further projection
currently occurs, but would be
+ /// useful if plucking values from a struct, e.g. getting `a.b.c.e` from
`a.b.c.{d, e}`.
pub fn try_new(
reader: R,
schema: SchemaRef,
batch_size: usize,
projection: Option<Vec<String>>,
) -> Result<Self> {
+ let projected_schema = if let Some(proj) = &projection {
+ if !proj.is_empty() {
+ let projected_fields: Vec<arrow::datatypes::Field> = proj
+ .iter()
+ .filter_map(|name| schema.column_with_name(name))
+ .map(|(_, field)| field.clone())
+ .collect();
+ Arc::new(arrow::datatypes::Schema::new(projected_fields))
+ } else {
+ Arc::clone(&schema)
+ }
+ } else {
+ Arc::clone(&schema)
+ };
Review Comment:
```suggestion
let projected_schema = projection.as_ref().filter(|p|
!p.is_empty()).map_or_else(
|| Arc::clone(&schema),
|proj| {
Arc::new(arrow::datatypes::Schema::new(
proj.iter()
.filter_map(|name| schema.column_with_name(name).map(|(_,
f)| f.clone()))
.collect(),
))
},
);
```
would be that more concise? I didn't check the snippet just the idea
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