improve docs

Author: alamb

datafusion/physical-plan/src/joins/cross_join.rs

@@ -49,9 +49,14 @@ use futures::{ready, Stream, StreamExt, TryStreamExt};
 /// Data of the left side
 type JoinLeftData = (RecordBatch, MemoryReservation);
 
+#[allow(rustdoc::private_intra_doc_links)]
 /// executes partitions in parallel and combines them into a set of
 /// partitions by combining all values from the left with all values on the right
-#[derive(Debug)] // note not Clone because of the OnceAsync
+///
+/// Note that the `Clone` trait is not implemented for this struct due to the
+/// `left_fut` [`OnceAsync`], which is used to coordinate the loading of the
+/// left side with the processing in each output stream.
+#[derive(Debug)]
 pub struct CrossJoinExec {
     /// left (build) side which gets loaded in memory
     pub left: Arc<dyn ExecutionPlan>,

datafusion/physical-plan/src/joins/hash_join.rs

@@ -136,6 +136,7 @@ impl JoinLeftData {
     }
 }
 
+#[allow(rustdoc::private_intra_doc_links)]
 /// Join execution plan: Evaluates eqijoin predicates in parallel on multiple
 /// partitions using a hash table and an optional filter list to apply post
 /// join.
@@ -293,7 +294,11 @@ impl JoinLeftData {
 ///                       │  "dimension"  │     │    "fact"     │
 ///                       └───────────────┘     └───────────────┘
 /// ```
-#[derive(Debug)] // note not Clone because of the OnceAsync
+///
+/// Note that the `Clone` trait is not implemented for this struct due to the
+/// `left_fut` [`OnceAsync`], which is used to coordinate the loading of the
+/// left side with the processing in each output stream.
+#[derive(Debug)]
 pub struct HashJoinExec {
     /// left (build) side which gets hashed
     pub left: Arc<dyn ExecutionPlan>,

datafusion/physical-plan/src/joins/nested_loop_join.rs

@@ -105,6 +105,7 @@ impl JoinLeftData {
     }
 }
 
+#[allow(rustdoc::private_intra_doc_links)]
 /// NestedLoopJoinExec is build-probe join operator, whose main task is to
 /// perform joins without any equijoin conditions in `ON` clause.
 ///
@@ -140,7 +141,10 @@ impl JoinLeftData {
 /// "reports" about probe phase completion (which means that "visited" bitmap won't be
 /// updated anymore), and only the last thread, reporting about completion, will return output.
 ///
-#[derive(Debug)] // note not Clone because of the OnceAsync
+/// Note that the `Clone` trait is not implemented for this struct due to the
+/// `left_fut` [`OnceAsync`], which is used to coordinate the loading of the
+/// left side with the processing in each output stream.
+#[derive(Debug)]
 pub struct NestedLoopJoinExec {
     /// left side
     pub(crate) left: Arc<dyn ExecutionPlan>,