comphead commented on code in PR #10647:
URL: https://github.com/apache/datafusion/pull/10647#discussion_r1614830679
##########
datafusion/core/src/datasource/physical_plan/parquet/schema_adapter.rs:
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@@ -20,35 +20,38 @@ use arrow_schema::{Schema, SchemaRef};
use std::fmt::Debug;
use std::sync::Arc;
-/// Factory of schema adapters.
+/// Factory for creating [`SchemaAdapter`]
///
-/// Provides means to implement custom schema adaptation.
+/// This interface provides a way to implement custom schema adaptation logic
+/// for ParquetExec (for example, to fill missing columns with default value
+/// other than null)
pub trait SchemaAdapterFactory: Debug + Send + Sync + 'static {
/// Provides `SchemaAdapter` for the ParquetExec.
fn create(&self, schema: SchemaRef) -> Box<dyn SchemaAdapter>;
}
-/// A utility which can adapt file-level record batches to a table schema
which may have a schema
+/// Adapt file-level [`RecordBatch`]es to a table schema, which may have a
schema
/// obtained from merging multiple file-level schemas.
///
/// This is useful for enabling schema evolution in partitioned datasets.
///
/// This has to be done in two stages.
///
-/// 1. Before reading the file, we have to map projected column indexes from
the table schema to
-/// the file schema.
+/// 1. Before reading the file, we have to map projected column indexes from
the
+/// table schema to the file schema.
///
-/// 2. After reading a record batch we need to map the read columns back to
the expected columns
-/// indexes and insert null-valued columns wherever the file schema was
missing a colum present
-/// in the table schema.
+/// 2. After reading a record batch map the read columns back to the expected
+/// columns indexes and insert null-valued columns wherever the file schema
was
+/// missing a colum present in the table schema.
Review Comment:
```suggestion
/// missing a column present in the table schema.
```
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