diff --git a/datafusion/physical-plan/src/joins/hash_join.rs b/datafusion/physical-plan/src/joins/hash_join.rs
index 2f1d652c8b97..5f52fa370bf5 100644
--- a/datafusion/physical-plan/src/joins/hash_join.rs
+++ b/datafusion/physical-plan/src/joins/hash_join.rs
@@ -625,7 +625,7 @@ impl ExecutionPlan for HashJoinExec {
             null_equals_null: self.null_equals_null,
             reservation,
             state: HashJoinStreamState::WaitBuildSide,
-            build_side_state: BuildSideState::Initial(BuildSideInitialState { left_fut }),
+            build_side: BuildSide::Initial(BuildSideInitialState { left_fut }),
         }))
     }
 
@@ -788,51 +788,58 @@ where
     Ok(())
 }
 
-/// Represents state of HashJoin build-side.
-enum BuildSideState {
+/// Represents build-side of hash join.
+enum BuildSide {
     /// Indicates that build-side not collected yet
     Initial(BuildSideInitialState),
     /// Indicates that build-side data has been collected
     Ready(BuildSideReadyState),
 }
 
+/// Container for BuildSide::Initial related data
 struct BuildSideInitialState {
+    /// Future for building hash table from build-side input
     left_fut: OnceFut<JoinLeftData>,
 }
 
+/// Container for BuildSide::Ready related data
 struct BuildSideReadyState {
+    /// Collected build-side data
     left_data: Arc<JoinLeftData>,
+    /// Which build-side rows have been matched while creating output.
+    /// For some OUTER joins, we need to know which rows have not been matched
+    /// to produce the correct output.
     visited_left_side: BooleanBufferBuilder,
 }
 
-impl BuildSideState {
-    /// Tries to extract BuildSideInitialState from BuildSideState enum.
+impl BuildSide {
+    /// Tries to extract BuildSideInitialState from BuildSide enum.
     /// Returns an error if state is not Initial.
     fn try_into_initial_mut(&mut self) -> Result<&mut BuildSideInitialState> {
         match self {
-            BuildSideState::Initial(state) => Ok(state),
+            BuildSide::Initial(state) => Ok(state),
             _ => Err(DataFusionError::Internal(
                 "Expected build side in initial state".to_string(),
             )),
         }
     }
 
-    /// Tries to extract BuildSideReadyState from BuildSideState enum.
+    /// Tries to extract BuildSideReadyState from BuildSide enum.
     /// Returns an error if state is not Ready.
     fn try_into_ready(&self) -> Result<&BuildSideReadyState> {
         match self {
-            BuildSideState::Ready(state) => Ok(state),
+            BuildSide::Ready(state) => Ok(state),
             _ => Err(DataFusionError::Internal(
                 "Expected build side in ready state".to_string(),
             )),
         }
     }
 
-    /// Tries to extract BuildSideReadyState from BuildSideState enum.
+    /// Tries to extract BuildSideReadyState from BuildSide enum.
     /// Returns an error if state is not Ready.
     fn try_into_ready_mut(&mut self) -> Result<&mut BuildSideReadyState> {
         match self {
-            BuildSideState::Ready(state) => Ok(state),
+            BuildSide::Ready(state) => Ok(state),
             _ => Err(DataFusionError::Internal(
                 "Expected build side in ready state".to_string(),
             )),
@@ -854,11 +861,15 @@ enum HashJoinStreamState {
     Completed,
 }
 
+/// Container for HashJoinStreamState::ProcessProbeBatch related data
 struct ProcessProbeBatchState {
+    /// Current probe-side batch
     batch: RecordBatch,
 }
 
 impl HashJoinStreamState {
+    /// Tries to extract ProcessProbeBatchState from HashJoinStreamState enum.
+    /// Returns an error if state is not ProcessProbeBatchState.
     fn try_as_process_probe_batch(&self) -> Result<&ProcessProbeBatchState> {
         match self {
             HashJoinStreamState::ProcessProbeBatch(state) => Ok(state),
@@ -900,10 +911,10 @@ struct HashJoinStream {
     null_equals_null: bool,
     /// Memory reservation
     reservation: MemoryReservation,
-    /// Stream state
+    /// State of the stream
     state: HashJoinStreamState,
-    /// Build side state
-    build_side_state: BuildSideState,
+    /// Build side
+    build_side: BuildSide,
 }
 
 impl RecordBatchStream for HashJoinStream {
@@ -1179,9 +1190,9 @@ impl HashJoinStream {
         }
     }
 
-    /// Collects build-side data by polling `OnceFut` future from initial build-side state
+    /// Collects build-side data by polling `OnceFut` future from initialized build-side
     ///
-    /// Updates build-side state to `Ready`, and state to `FetchProbeSide`
+    /// Updates build-side to `Ready`, and state to `FetchProbeSide`
     fn collect_build_side(
         &mut self,
         cx: &mut std::task::Context<'_>,
@@ -1189,7 +1200,7 @@ impl HashJoinStream {
         let build_timer = self.join_metrics.build_time.timer();
         // build hash table from left (build) side, if not yet done
         let left_data = ready!(self
-            .build_side_state
+            .build_side
             .try_into_initial_mut()?
             .left_fut
             .get_shared(cx))?;
@@ -1220,7 +1231,7 @@ impl HashJoinStream {
         };
 
         self.state = HashJoinStreamState::FetchProbeBatch;
-        self.build_side_state = BuildSideState::Ready(BuildSideReadyState {
+        self.build_side = BuildSide::Ready(BuildSideReadyState {
             left_data,
             visited_left_side,
         });
@@ -1259,7 +1270,7 @@ impl HashJoinStream {
         &mut self,
     ) -> Result<StatefulStreamResult<Option<RecordBatch>>> {
         let state = self.state.try_as_process_probe_batch()?;
-        let build_side = self.build_side_state.try_into_ready_mut()?;
+        let build_side = self.build_side.try_into_ready_mut()?;
 
         self.join_metrics.input_batches.add(1);
         self.join_metrics.input_rows.add(state.batch.num_rows());
@@ -1337,7 +1348,7 @@ impl HashJoinStream {
             return Ok(StatefulStreamResult::Continue);
         }
 
-        let build_side = self.build_side_state.try_into_ready()?;
+        let build_side = self.build_side.try_into_ready()?;
 
         // use the global left bitmap to produce the left indices and right indices
         let (left_side, right_side) =
diff --git a/datafusion/physical-plan/src/joins/utils.rs b/datafusion/physical-plan/src/joins/utils.rs
index 26fb26d283ee..eae65ce9c26b 100644
--- a/datafusion/physical-plan/src/joins/utils.rs
+++ b/datafusion/physical-plan/src/joins/utils.rs
@@ -850,19 +850,18 @@ impl<T: 'static> OnceFut<T> {
         }
     }
 
-    /// Get the result of the computation as a shared reference if it is ready, without consuming it
+    /// Get shared reference to the result of the computation if it is ready, without consuming it
     pub(crate) fn get_shared(&mut self, cx: &mut Context<'_>) -> Poll<Result<Arc<T>>> {
         if let OnceFutState::Pending(fut) = &mut self.state {
             let r = ready!(fut.poll_unpin(cx));
             self.state = OnceFutState::Ready(r);
         }
 
-        // Cannot use loop as this would trip up the borrow checker
         match &self.state {
             OnceFutState::Pending(_) => unreachable!(),
             OnceFutState::Ready(r) => Poll::Ready(
                 r.clone()
-                    .map_err(|e| DataFusionError::External(Box::new(e.clone()))),
+                    .map_err(|e| DataFusionError::External(Box::new(e))),
             ),
         }
     }