From 3d9f9ea53e0b1762278c5496b185021b32241ea3 Mon Sep 17 00:00:00 2001
From: Edd Robinson <me@edd.io>
Date: Thu, 21 Oct 2021 10:17:41 +0100
Subject: [PATCH 1/3] refactor: use Expr Display impl

---
 predicate/src/predicate.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/predicate/src/predicate.rs b/predicate/src/predicate.rs
index d7f3b624b3..cc7c590c21 100644
--- a/predicate/src/predicate.rs
+++ b/predicate/src/predicate.rs
@@ -234,12 +234,15 @@ impl fmt::Display for Predicate {
         }
 
         if !self.exprs.is_empty() {
-            // Expr doesn't implement `Display` yet, so just the debug version
-            // See https://github.com/apache/arrow-datafusion/issues/347
-            let display_exprs = self.exprs.iter().map(|e| format!("{:?}", e));
-            write!(f, " exprs: [{}]", iter_to_str(display_exprs))?;
+            write!(f, " exprs: [")?;
+            for (i, expr) in self.exprs.iter().enumerate() {
+                write!(f, "{}", expr)?;
+                if i < self.exprs.len() - 1 {
+                    write!(f, " ")?;
+                }
+            }
+            write!(f, "]")?;
         }
-
         Ok(())
     }
 }

From a3e750c9fcca211cf528574fa39f75bab5889870 Mon Sep 17 00:00:00 2001
From: Edd Robinson <me@edd.io>
Date: Fri, 22 Oct 2021 11:27:06 +0100
Subject: [PATCH 2/3] test: add null column to test

---
 read_buffer/src/chunk.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/read_buffer/src/chunk.rs b/read_buffer/src/chunk.rs
index 94ac209ba4..f6e7df7cb1 100644
--- a/read_buffer/src/chunk.rs
+++ b/read_buffer/src/chunk.rs
@@ -974,6 +974,7 @@ mod test {
                 .field("sketchy_sensor", Int64)
                 .non_null_field("active", Boolean)
                 .field("msg", Utf8)
+                .field("all_null", Utf8)
                 .timestamp()
                 .build()
                 .unwrap();
@@ -997,6 +998,7 @@ mod test {
                     Some("message b"),
                     None,
                 ])),
+                Arc::new(StringArray::from(vec![None, None, None])),
                 Arc::new(TimestampNanosecondArray::from_vec(
                     vec![i, 2 * i, 3 * i],
                     None,
@@ -1058,6 +1060,7 @@ mod test {
         );
         assert_rb_column_equals(&first_row_group, "active", &exp_active_values);
         assert_rb_column_equals(&first_row_group, "msg", &exp_msg_values);
+        assert_rb_column_equals(&first_row_group, "all_null", &Values::String(vec![None]));
         assert_rb_column_equals(&first_row_group, "time", &Values::I64(vec![100])); // first row from first record batch
 
         let second_row_group = itr.next().unwrap();
@@ -1070,8 +1073,16 @@ mod test {
             &exp_sketchy_sensor_values,
         );
         assert_rb_column_equals(&first_row_group, "active", &exp_active_values);
+        assert_rb_column_equals(&first_row_group, "all_null", &Values::String(vec![None]));
         assert_rb_column_equals(&second_row_group, "time", &Values::I64(vec![200])); // first row from second record batch
 
+        // No rows returned when filtering on all_null column
+        let predicate = Predicate::new(vec![BinaryExpr::from(("all_null", "!=", "a string"))]);
+        let mut itr = chunk
+            .read_filter(predicate, Selection::All, vec![])
+            .unwrap();
+        assert!(itr.next().is_none());
+
         // Error when predicate is invalid
         let predicate =
             Predicate::with_time_range(&[BinaryExpr::from(("env", "=", 22.3))], 100, 205);

From 84a00cd5b69cbc31e22f63d87fac31684d2bad80 Mon Sep 17 00:00:00 2001
From: Edd Robinson <me@edd.io>
Date: Fri, 22 Oct 2021 15:35:24 +0100
Subject: [PATCH 3/3] refactor: comma

---
 predicate/src/predicate.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/predicate/src/predicate.rs b/predicate/src/predicate.rs
index cc7c590c21..b0d6dcf910 100644
--- a/predicate/src/predicate.rs
+++ b/predicate/src/predicate.rs
@@ -238,7 +238,7 @@ impl fmt::Display for Predicate {
             for (i, expr) in self.exprs.iter().enumerate() {
                 write!(f, "{}", expr)?;
                 if i < self.exprs.len() - 1 {
-                    write!(f, " ")?;
+                    write!(f, ", ")?;
                 }
             }
             write!(f, "]")?;