From 737c3fcb14b28cce2ff92dcd8915711129e91ecf Mon Sep 17 00:00:00 2001
From: Jorge Leitao <jorgecarleitao@gmail.com>
Date: Sun, 30 Oct 2022 23:00:59 +0100
Subject: [PATCH] Optimized slicing (#1285)

Optimized slice
---
 src/array/binary/mod.rs            | 3 ++-
 src/array/boolean/mod.rs           | 3 ++-
 src/array/fixed_size_binary/mod.rs | 3 ++-
 src/array/fixed_size_list/mod.rs   | 3 ++-
 src/array/list/mod.rs              | 3 ++-
 src/array/map/mod.rs               | 3 ++-
 src/array/primitive/mod.rs         | 3 ++-
 src/array/struct_/mod.rs           | 3 ++-
 src/array/utf8/mod.rs              | 3 ++-
 9 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/array/binary/mod.rs b/src/array/binary/mod.rs
index 9697446a63b..72341bdfeeb 100644
--- a/src/array/binary/mod.rs
+++ b/src/array/binary/mod.rs
@@ -203,7 +203,8 @@ impl<O: Offset> BinaryArray<O> {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         let offsets = self.offsets.clone().slice_unchecked(offset, length + 1);
         Self {
             data_type: self.data_type.clone(),
diff --git a/src/array/boolean/mod.rs b/src/array/boolean/mod.rs
index a3788b9b856..1d364cfe567 100644
--- a/src/array/boolean/mod.rs
+++ b/src/array/boolean/mod.rs
@@ -164,7 +164,8 @@ impl BooleanArray {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         Self {
             data_type: self.data_type.clone(),
             values: self.values.clone().slice_unchecked(offset, length),
diff --git a/src/array/fixed_size_binary/mod.rs b/src/array/fixed_size_binary/mod.rs
index ab1a28beb08..d467d2c3c00 100644
--- a/src/array/fixed_size_binary/mod.rs
+++ b/src/array/fixed_size_binary/mod.rs
@@ -131,7 +131,8 @@ impl FixedSizeBinaryArray {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         let values = self
             .values
             .clone()
diff --git a/src/array/fixed_size_list/mod.rs b/src/array/fixed_size_list/mod.rs
index dac5f19c70a..c603f6bf6aa 100644
--- a/src/array/fixed_size_list/mod.rs
+++ b/src/array/fixed_size_list/mod.rs
@@ -150,7 +150,8 @@ impl FixedSizeListArray {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         let values = self
             .values
             .clone()
diff --git a/src/array/list/mod.rs b/src/array/list/mod.rs
index 819f6b1dd20..feb5a5df93b 100644
--- a/src/array/list/mod.rs
+++ b/src/array/list/mod.rs
@@ -222,7 +222,8 @@ impl<O: Offset> ListArray<O> {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         let offsets = self.offsets.clone().slice_unchecked(offset, length + 1);
         Self {
             data_type: self.data_type.clone(),
diff --git a/src/array/map/mod.rs b/src/array/map/mod.rs
index cc8a02c7ccd..51ca56a8459 100644
--- a/src/array/map/mod.rs
+++ b/src/array/map/mod.rs
@@ -167,7 +167,8 @@ impl MapArray {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         Self {
             data_type: self.data_type.clone(),
             offsets,
diff --git a/src/array/primitive/mod.rs b/src/array/primitive/mod.rs
index a64cd90f38a..6b62fe220cd 100644
--- a/src/array/primitive/mod.rs
+++ b/src/array/primitive/mod.rs
@@ -230,7 +230,8 @@ impl<T: NativeType> PrimitiveArray<T> {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         Self {
             data_type: self.data_type.clone(),
             values: self.values.clone().slice_unchecked(offset, length),
diff --git a/src/array/struct_/mod.rs b/src/array/struct_/mod.rs
index 3fb7be0c7b1..a371147f3d8 100644
--- a/src/array/struct_/mod.rs
+++ b/src/array/struct_/mod.rs
@@ -198,7 +198,8 @@ impl StructArray {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         Self {
             data_type: self.data_type.clone(),
             values: self
diff --git a/src/array/utf8/mod.rs b/src/array/utf8/mod.rs
index 5e057e90a5b..965eb6552f1 100644
--- a/src/array/utf8/mod.rs
+++ b/src/array/utf8/mod.rs
@@ -220,7 +220,8 @@ impl<O: Offset> Utf8Array<O> {
         let validity = self
             .validity
             .clone()
-            .map(|x| x.slice_unchecked(offset, length));
+            .map(|bitmap| bitmap.slice_unchecked(offset, length))
+            .and_then(|bitmap| (bitmap.unset_bits() > 0).then(|| bitmap));
         // + 1: `length == 0` implies that we take the first offset.
         let offsets = self.offsets.clone().slice_unchecked(offset, length + 1);
         Self {