diff --git a/src/array/growable/utils.rs b/src/array/growable/utils.rs
index 4afdc1a05ea..6a67988e2d8 100644
--- a/src/array/growable/utils.rs
+++ b/src/array/growable/utils.rs
@@ -46,10 +46,8 @@ pub(super) fn extend_validity(
 ) {
     if let Some(bitmap) = validity {
         assert!(start + len <= bitmap.len());
-        unsafe {
-            let iter = (start..start + len).map(|i| bitmap.get_bit_unchecked(i));
-            mutable_validity.extend_from_trusted_len_iter_unchecked(iter);
-        };
+        let (slice, offset, _) = bitmap.as_slice();
+        mutable_validity.extend_from_slice(slice, start + offset, len);
     } else if use_validity {
         mutable_validity.extend_constant(len, true);
     };
diff --git a/src/bitmap/mutable.rs b/src/bitmap/mutable.rs
index fa5cba54fb2..bd6a183f0b0 100644
--- a/src/bitmap/mutable.rs
+++ b/src/bitmap/mutable.rs
@@ -131,16 +131,63 @@ impl MutableBitmap {
         self.length = len;
     }
 
+    fn extend_set(&mut self, mut additional: usize) {
+        let offset = self.length % 8;
+        let added = if offset != 0 {
+            // offset != 0 => at least one byte in the buffer
+            let last_index = self.buffer.len() - 1;
+            let last = &mut self.buffer[last_index];
+
+            let remaining = 0b11111111u8;
+            let remaining = remaining >> 8usize.saturating_sub(additional);
+            let remaining = remaining << offset;
+            *last |= remaining;
+            std::cmp::min(additional, 8 - offset)
+        } else {
+            0
+        };
+        self.length += added;
+        additional = additional.saturating_sub(added);
+        if additional > 0 {
+            debug_assert_eq!(self.length % 8, 0);
+            let existing = self.buffer.len();
+            let required = (self.length + additional).saturating_add(7) / 8;
+            // add remaining as full bytes
+            self.buffer.extend_from_trusted_len_iter(
+                std::iter::repeat(0b11111111u8).take(required - existing),
+            );
+            self.length += additional;
+        }
+    }
+
+    fn extend_unset(&mut self, mut additional: usize) {
+        let offset = self.length % 8;
+        let added = if offset != 0 {
+            // offset != 0 => at least one byte in the buffer
+            let last_index = self.buffer.len() - 1;
+            let last = &mut self.buffer[last_index];
+            *last &= 0b11111111u8 >> (8 - offset); // unset them
+            std::cmp::min(additional, 8 - offset)
+        } else {
+            0
+        };
+        self.length += added;
+        additional = additional.saturating_sub(added);
+        if additional > 0 {
+            debug_assert_eq!(self.length % 8, 0);
+            self.buffer
+                .resize((self.length + additional).saturating_add(7) / 8, 0);
+            self.length += additional;
+        }
+    }
+
     /// Extends [`MutableBitmap`] by `additional` values of constant `value`.
     #[inline]
     pub fn extend_constant(&mut self, additional: usize, value: bool) {
         if value {
-            let iter = std::iter::repeat(true).take(additional);
-            self.extend_from_trusted_len_iter(iter);
+            self.extend_set(additional)
         } else {
-            self.buffer
-                .resize((self.length + additional).saturating_add(7) / 8, 0);
-            self.length += additional;
+            self.extend_unset(additional)
         }
     }
 
diff --git a/src/compute/mod.rs b/src/compute/mod.rs
index 332905b405d..232677e2679 100644
--- a/src/compute/mod.rs
+++ b/src/compute/mod.rs
@@ -7,13 +7,6 @@
 //! Some dynamically-typed operators have an auxiliary function, `can_*`, that returns
 //! true if the operator can be applied to the particular `DataType`.
 
-pub mod aggregate;
-pub mod arithmetics;
-pub mod arity;
-pub mod boolean;
-pub mod boolean_kleene;
-pub mod cast;
-pub mod comparison;
 pub mod concat;
 pub mod contains;
 pub mod filter;
diff --git a/tests/it/bitmap/mutable.rs b/tests/it/bitmap/mutable.rs
index 2704f4c1f07..7acf4781666 100644
--- a/tests/it/bitmap/mutable.rs
+++ b/tests/it/bitmap/mutable.rs
@@ -201,3 +201,49 @@ fn debug() {
     b.push(true);
     assert_eq!(format!("{:?}", b), "[0b11000001, 0b_______1]");
 }
+
+#[test]
+fn extend_set() {
+    let mut b = MutableBitmap::new();
+    b.extend_constant(6, true);
+    assert_eq!(b.as_slice(), &[0b11111111]);
+    assert_eq!(b.len(), 6);
+
+    let mut b = MutableBitmap::from(&[false]);
+    b.extend_constant(6, true);
+    assert_eq!(b.as_slice(), &[0b01111110]);
+    assert_eq!(b.len(), 1 + 6);
+
+    let mut b = MutableBitmap::from(&[false]);
+    b.extend_constant(9, true);
+    assert_eq!(b.as_slice(), &[0b11111110, 0b11111111]);
+    assert_eq!(b.len(), 1 + 9);
+
+    let mut b = MutableBitmap::from(&[false, false, false, false]);
+    b.extend_constant(2, true);
+    assert_eq!(b.as_slice(), &[0b00110000]);
+    assert_eq!(b.len(), 4 + 2);
+}
+
+#[test]
+fn extend_unset() {
+    let mut b = MutableBitmap::new();
+    b.extend_constant(6, false);
+    assert_eq!(b.as_slice(), &[0b0000000]);
+    assert_eq!(b.len(), 6);
+
+    let mut b = MutableBitmap::from(&[true]);
+    b.extend_constant(6, false);
+    assert_eq!(b.as_slice(), &[0b00000001]);
+    assert_eq!(b.len(), 1 + 6);
+
+    let mut b = MutableBitmap::from(&[true]);
+    b.extend_constant(9, false);
+    assert_eq!(b.as_slice(), &[0b0000001, 0b00000000]);
+    assert_eq!(b.len(), 1 + 9);
+
+    let mut b = MutableBitmap::from(&[true, true, true, true]);
+    b.extend_constant(2, false);
+    assert_eq!(b.as_slice(), &[0b00001111]);
+    assert_eq!(b.len(), 4 + 2);
+}