perf: avoid boundary checks on accessing array items (#7570)

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

src/common/function/src/aggrs/count_hash.rs

@@ -453,8 +453,8 @@ impl Accumulator for CountHashAccumulator {
                 );
             };
             let hash_array = inner_array.as_any().downcast_ref::<UInt64Array>().unwrap();
-            for i in 0..hash_array.len() {
-                self.values.insert(hash_array.value(i));
+            for &hash in hash_array.values().iter().take(hash_array.len()) {
+                self.values.insert(hash);
             }
         }
         Ok(())

src/common/function/src/aggrs/geo/encoding.rs

@@ -152,9 +152,9 @@ impl DfAccumulator for JsonEncodePathAccumulator {
         let lng_array = lng_array.as_primitive::<Float64Type>();
 
         let mut coords = Vec::with_capacity(len);
-        for i in 0..len {
-            let lng = lng_array.value(i);
-            let lat = lat_array.value(i);
+        let lng_values = lng_array.values();
+        let lat_values = lat_array.values();
+        for (&lng, &lat) in lng_values.iter().zip(lat_values.iter()).take(len) {
             coords.push(vec![lng, lat]);
         }
 

src/common/function/src/scalars/primary_key.rs

@@ -208,9 +208,9 @@ fn decode_dictionary(
 
     let mut rows = Vec::with_capacity(number_rows);
     let keys = dict.keys();
-    for i in 0..number_rows {
-        let dict_index = keys.value(i) as usize;
-        rows.push(decoded_values[dict_index].clone());
+    let dict_indices = keys.values();
+    for &dict_index in dict_indices[..number_rows].iter() {
+        rows.push(decoded_values[dict_index as usize].clone());
     }
 
     Ok(rows)

src/datatypes/src/vectors/dictionary.rs

@@ -170,11 +170,12 @@ impl<K: ArrowDictionaryKeyType> Serializable for DictionaryVector<K> {
         // the value it refers to in the dictionary
         let mut result = Vec::with_capacity(self.len());
 
-        for i in 0..self.len() {
+        let keys = self.array.keys();
+        let key_values = &keys.values()[..self.len()];
+        for (i, &key) in key_values.iter().enumerate() {
             if self.is_null(i) {
                 result.push(JsonValue::Null);
             } else {
-                let key = self.array.keys().value(i);
                 let value = self.item_vector.get(key.as_usize());
                 let json_value = serde_json::to_value(value).context(error::SerializeSnafu)?;
                 result.push(json_value);
@@ -247,16 +248,9 @@ impl<K: ArrowDictionaryKeyType> VectorOp for DictionaryVector<K> {
         let mut replicated_keys = PrimitiveBuilder::new();
 
         let mut previous_offset = 0;
-        for (i, &offset) in offsets.iter().enumerate() {
-            let key = if i < self.len() {
-                if keys.is_valid(i) {
-                    Some(keys.value(i))
-                } else {
-                    None
-                }
-            } else {
-                None
-            };
+        let mut key_iter = keys.iter().chain(std::iter::repeat(None));
+        for &offset in offsets {
+            let key = key_iter.next().unwrap();
 
             // repeat this key (offset - previous_offset) times
             let repeat_count = offset - previous_offset;

src/mito2/src/sst/index.rs

@@ -1174,9 +1174,8 @@ pub(crate) fn decode_primary_keys_with_counts(
     let mut result: Vec<(CompositeValues, usize)> = Vec::new();
     let mut prev_key: Option<u32> = None;
 
-    for i in 0..keys.len() {
-        let current_key = keys.value(i);
-
+    let pk_indices = keys.values();
+    for &current_key in pk_indices.iter().take(keys.len()) {
         // Checks if current key is the same as previous key
         if let Some(prev) = prev_key
             && prev == current_key

src/mito2/src/sst/parquet/flat_format.rs

@@ -563,9 +563,8 @@ pub(crate) fn decode_primary_keys(
 
     // The parquet reader may read the whole dictionary page into the dictionary values, so
     // we may decode many primary keys not in this batch if we decode the values array directly.
-    for i in 0..keys.len() {
-        let current_key = keys.value(i);
-
+    let pk_indices = keys.values();
+    for &current_key in pk_indices.iter().take(keys.len()) {
         // Check if current key is the same as previous key
         if let Some(prev) = prev_key
             && prev == current_key