Require Debug for DataSource (#14882)

* Require `Debug` for `DataSource`

* Add a note about why having Debug is useful

Author: alamb

datafusion/datasource/src/memory.rs

@@ -346,7 +346,7 @@ impl MemoryExec {
 }
 
 /// Data source configuration for reading in-memory batches of data
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct MemorySourceConfig {
     /// The partitions to query
     partitions: Vec<Vec<RecordBatch>>,

datafusion/datasource/src/source.rs

@@ -35,7 +35,9 @@ use datafusion_physical_expr_common::sort_expr::LexOrdering;
 
 /// Common behaviors in Data Sources for both from Files and Memory.
 /// See `DataSourceExec` for physical plan implementation
-pub trait DataSource: Send + Sync {
+///
+/// Requires `Debug` to assist debugging
+pub trait DataSource: Send + Sync + Debug {
     fn open(
         &self,
         partition: usize,
@@ -66,12 +68,6 @@ pub trait DataSource: Send + Sync {
     ) -> datafusion_common::Result<Option<Arc<dyn ExecutionPlan>>>;
 }
 
-impl Debug for dyn DataSource {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "DataSource: ")
-    }
-}
-
 /// Unified data source for file formats like JSON, CSV, AVRO, ARROW, PARQUET
 #[derive(Clone, Debug)]
 pub struct DataSourceExec {