From df74a153eb8a40cc6b6594b6ceb85e927acaf332 Mon Sep 17 00:00:00 2001
From: Qingping Hou <dave2008713@gmail.com>
Date: Sat, 10 Jul 2021 14:32:53 -0700
Subject: [PATCH 1/2] replace once iter chain with array::IntoIter

---
 datafusion/src/logical_plan/plan.rs          |  8 +++-----
 datafusion/src/optimizer/filter_push_down.rs | 13 +++++++++----
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/datafusion/src/logical_plan/plan.rs b/datafusion/src/logical_plan/plan.rs
index b954b6a97950..87fc64a010a6 100644
--- a/datafusion/src/logical_plan/plan.rs
+++ b/datafusion/src/logical_plan/plan.rs
@@ -375,12 +375,10 @@ impl LogicalPlan {
                 {
                     self.using_columns.push(
                         on.iter()
-                            .map(|entry| {
-                                std::iter::once(entry.0.clone())
-                                    .chain(std::iter::once(entry.1.clone()))
-                            })
+                            .map(|entry| std::array::IntoIter::new([&entry.0, &entry.1]))
                             .flatten()
-                            .collect::<HashSet<_>>(),
+                            .cloned()
+                            .collect::<HashSet<Column>>(),
                     );
                 }
                 Ok(true)
diff --git a/datafusion/src/optimizer/filter_push_down.rs b/datafusion/src/optimizer/filter_push_down.rs
index 76d8c05bed4c..2d87b5a44c8f 100644
--- a/datafusion/src/optimizer/filter_push_down.rs
+++ b/datafusion/src/optimizer/filter_push_down.rs
@@ -97,9 +97,11 @@ fn get_join_predicates<'a>(
         .fields()
         .iter()
         .map(|f| {
-            std::iter::once(f.qualified_column())
+            std::array::IntoIter::new([
+                f.qualified_column(),
                 // we need to push down filter using unqualified column as well
-                .chain(std::iter::once(f.unqualified_column()))
+                f.unqualified_column(),
+            ])
         })
         .flatten()
         .collect::<HashSet<_>>();
@@ -107,8 +109,11 @@ fn get_join_predicates<'a>(
         .fields()
         .iter()
         .map(|f| {
-            std::iter::once(f.qualified_column())
-                .chain(std::iter::once(f.unqualified_column()))
+            std::array::IntoIter::new([
+                f.qualified_column(),
+                // we need to push down filter using unqualified column as well
+                f.unqualified_column(),
+            ])
         })
         .flatten()
         .collect::<HashSet<_>>();

From 8e8b2e740a04ca69cebd186e9cbfc66ecb65b04f Mon Sep 17 00:00:00 2001
From: Qingping Hou <dave2008713@gmail.com>
Date: Mon, 12 Jul 2021 22:14:15 -0700
Subject: [PATCH 2/2] use new array IntoIter implementation from rust 1.53

---
 datafusion/src/logical_plan/plan.rs          | 2 +-
 datafusion/src/optimizer/filter_push_down.rs | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/datafusion/src/logical_plan/plan.rs b/datafusion/src/logical_plan/plan.rs
index 87fc64a010a6..fdf94809f16e 100644
--- a/datafusion/src/logical_plan/plan.rs
+++ b/datafusion/src/logical_plan/plan.rs
@@ -375,7 +375,7 @@ impl LogicalPlan {
                 {
                     self.using_columns.push(
                         on.iter()
-                            .map(|entry| std::array::IntoIter::new([&entry.0, &entry.1]))
+                            .map(|entry| [&entry.0, &entry.1])
                             .flatten()
                             .cloned()
                             .collect::<HashSet<Column>>(),
diff --git a/datafusion/src/optimizer/filter_push_down.rs b/datafusion/src/optimizer/filter_push_down.rs
index 2d87b5a44c8f..399923e87218 100644
--- a/datafusion/src/optimizer/filter_push_down.rs
+++ b/datafusion/src/optimizer/filter_push_down.rs
@@ -97,11 +97,11 @@ fn get_join_predicates<'a>(
         .fields()
         .iter()
         .map(|f| {
-            std::array::IntoIter::new([
+            [
                 f.qualified_column(),
                 // we need to push down filter using unqualified column as well
                 f.unqualified_column(),
-            ])
+            ]
         })
         .flatten()
         .collect::<HashSet<_>>();
@@ -109,11 +109,11 @@ fn get_join_predicates<'a>(
         .fields()
         .iter()
         .map(|f| {
-            std::array::IntoIter::new([
+            [
                 f.qualified_column(),
                 // we need to push down filter using unqualified column as well
                 f.unqualified_column(),
-            ])
+            ]
         })
         .flatten()
         .collect::<HashSet<_>>();