ARROW-10030: [Rust] Add support for FromIter and IntoIter for primitive types

rust/arrow/benches/cast_kernels.rs

@@ -29,100 +29,121 @@ use arrow::array::*;
 use arrow::compute::cast;
 use arrow::datatypes::*;
 
-// cast array from specified primitive array type to desired data type
-fn cast_array<FROM>(size: usize, to_type: DataType)
+fn build_array<FROM>(size: usize) -> ArrayRef
 where
     FROM: ArrowNumericType,
     Standard: Distribution<FROM::Native>,
-    PrimitiveArray<FROM>: std::convert::From<Vec<FROM::Native>>,
+    PrimitiveArray<FROM>: std::convert::From<Vec<Option<FROM::Native>>>,
 {
-    let array = Arc::new(PrimitiveArray::<FROM>::from(vec![
-        random::<FROM::Native>();
-        size
-    ])) as ArrayRef;
-    criterion::black_box(cast(&array, &to_type).unwrap());
+    let values = (0..size)
+        .map(|_| {
+            // 10% nulls, i.e. dense.
+            if random::<f64>() < 0.1 {
+                None
+            } else {
+                Some(random::<FROM::Native>())
+            }
+        })
+        .collect();
+
+    Arc::new(PrimitiveArray::<FROM>::from(values))
 }
 
-// cast timestamp array from specified primitive array type to desired data type
-fn cast_timestamp_array<FROM>(size: usize, to_type: DataType)
+fn build_timestamp_array<FROM>(size: usize) -> ArrayRef
 where
     FROM: ArrowTimestampType,
-    Standard: Distribution<i64>,
+    Standard: Distribution<FROM::Native>,
 {
-    let array = Arc::new(PrimitiveArray::<FROM>::from_vec(
-        vec![random::<i64>(); size],
-        None,
-    )) as ArrayRef;
-    criterion::black_box(cast(&array, &to_type).unwrap());
+    let values = (0..size)
+        .map(|_| {
+            if random::<f64>() < 0.5 {
+                None
+            } else {
+                Some(random::<i64>())
+            }
+        })
+        .collect::<Vec<Option<i64>>>();
+
+    Arc::new(PrimitiveArray::<FROM>::from_opt_vec(values, None))
+}
+
+// cast array from specified primitive array type to desired data type
+fn cast_array(array: &ArrayRef, to_type: DataType) {
+    criterion::black_box(cast(array, &to_type).unwrap());
 }
 
 fn add_benchmark(c: &mut Criterion) {
+    let i32_array = build_array::<Int32Type>(512);
+    let i64_array = build_array::<Int64Type>(512);
+    let f32_array = build_array::<Float32Type>(512);
+    let f64_array = build_array::<Float64Type>(512);
+    let date64_array = build_array::<Date64Type>(512);
+    let date32_array = build_array::<Date32Type>(512);
+    let time32s_array = build_array::<Time32SecondType>(512);
+    let time64ns_array = build_array::<Time64NanosecondType>(512);
+    let time_ns_array = build_timestamp_array::<TimestampNanosecondType>(512);
+    let time_ms_array = build_timestamp_array::<TimestampMillisecondType>(512);
+
     c.bench_function("cast int32 to int32 512", |b| {
-        b.iter(|| cast_array::<Int32Type>(512, DataType::Int32))
+        b.iter(|| cast_array(&i32_array, DataType::Int32))
     });
     c.bench_function("cast int32 to uint32 512", |b| {
-        b.iter(|| cast_array::<Int32Type>(512, DataType::UInt32))
+        b.iter(|| cast_array(&i32_array, DataType::UInt32))
     });
     c.bench_function("cast int32 to float32 512", |b| {
-        b.iter(|| cast_array::<Int32Type>(512, DataType::Float32))
+        b.iter(|| cast_array(&i32_array, DataType::Float32))
     });
     c.bench_function("cast int32 to float64 512", |b| {
-        b.iter(|| cast_array::<Int32Type>(512, DataType::Float64))
+        b.iter(|| cast_array(&i32_array, DataType::Float64))
     });
     c.bench_function("cast int32 to int64 512", |b| {
-        b.iter(|| cast_array::<Int32Type>(512, DataType::Int64))
+        b.iter(|| cast_array(&i32_array, DataType::Int64))
     });
     c.bench_function("cast float32 to int32 512", |b| {
-        b.iter(|| cast_array::<Float32Type>(512, DataType::Int32))
+        b.iter(|| cast_array(&f32_array, DataType::Int32))
     });
     c.bench_function("cast float64 to float32 512", |b| {
-        b.iter(|| cast_array::<Float64Type>(512, DataType::Float32))
+        b.iter(|| cast_array(&f64_array, DataType::Float32))
     });
     c.bench_function("cast float64 to uint64 512", |b| {
-        b.iter(|| cast_array::<Float64Type>(512, DataType::UInt64))
+        b.iter(|| cast_array(&f64_array, DataType::UInt64))
     });
     c.bench_function("cast int64 to int32 512", |b| {
-        b.iter(|| cast_array::<Int64Type>(512, DataType::Int32))
+        b.iter(|| cast_array(&i64_array, DataType::Int32))
     });
     c.bench_function("cast date64 to date32 512", |b| {
-        b.iter(|| cast_array::<Date64Type>(512, DataType::Date32(DateUnit::Day)))
+        b.iter(|| cast_array(&date64_array, DataType::Date32(DateUnit::Day)))
     });
     c.bench_function("cast date32 to date64 512", |b| {
-        b.iter(|| cast_array::<Date32Type>(512, DataType::Date64(DateUnit::Millisecond)))
+        b.iter(|| cast_array(&date32_array, DataType::Date64(DateUnit::Millisecond)))
     });
     c.bench_function("cast time32s to time32ms 512", |b| {
-        b.iter(|| {
-            cast_array::<Time32SecondType>(512, DataType::Time32(TimeUnit::Millisecond))
-        })
+        b.iter(|| cast_array(&time32s_array, DataType::Time32(TimeUnit::Millisecond)))
     });
     c.bench_function("cast time32s to time64us 512", |b| {
-        b.iter(|| {
-            cast_array::<Time32SecondType>(512, DataType::Time64(TimeUnit::Microsecond))
-        })
+        b.iter(|| cast_array(&time32s_array, DataType::Time64(TimeUnit::Microsecond)))
     });
     c.bench_function("cast time64ns to time32s 512", |b| {
-        b.iter(|| {
-            cast_array::<Time64NanosecondType>(512, DataType::Time32(TimeUnit::Second))
-        })
+        b.iter(|| cast_array(&time64ns_array, DataType::Time32(TimeUnit::Second)))
     });
     c.bench_function("cast timestamp_ns to timestamp_s 512", |b| {
         b.iter(|| {
-            cast_timestamp_array::<TimestampNanosecondType>(
-                512,
+            cast_array(
+                &time_ns_array,
                 DataType::Timestamp(TimeUnit::Nanosecond, None),
             )
         })
     });
     c.bench_function("cast timestamp_ms to timestamp_ns 512", |b| {
         b.iter(|| {
-            cast_timestamp_array::<TimestampMillisecondType>(
-                512,
+            cast_array(
+                &time_ms_array,
                 DataType::Timestamp(TimeUnit::Nanosecond, None),
             )
         })
     });
     c.bench_function("cast timestamp_ms to i64 512", |b| {
-        b.iter(|| cast_timestamp_array::<TimestampMillisecondType>(512, DataType::Int64))
+        b.iter(|| cast_array(&time_ms_array, DataType::Int64))
     });
 }
 

rust/arrow/src/array/array.rs

@@ -16,6 +16,7 @@
 // under the License.
 
 use std::any::Any;
+use std::borrow::Borrow;
 use std::convert::{From, TryFrom};
 use std::fmt;
 use std::io::Write;
@@ -693,6 +694,61 @@ impl fmt::Debug for PrimitiveArray<BooleanType> {
     }
 }
 
+impl<'a, T: ArrowPrimitiveType> IntoIterator for &'a PrimitiveArray<T> {
+    type Item = Option<<T as ArrowPrimitiveType>::Native>;
+    type IntoIter = PrimitiveIter<'a, T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        PrimitiveIter::<'a, T>::new(self)
+    }
+}
+
+impl<'a, T: ArrowPrimitiveType> PrimitiveArray<T> {
+    /// constructs a new iterator
+    pub fn iter(&'a self) -> PrimitiveIter<'a, T> {
+        PrimitiveIter::<'a, T>::new(&self)
+    }
+}
+
+impl<T: ArrowPrimitiveType, Ptr: Borrow<Option<<T as ArrowPrimitiveType>::Native>>>
+    FromIterator<Ptr> for PrimitiveArray<T>
+{
+    fn from_iter<I: IntoIterator<Item = Ptr>>(iter: I) -> Self {
+        let iter = iter.into_iter();
+        let (_, data_len) = iter.size_hint();
+        let data_len = data_len.unwrap(); // panic if no upper bound.
+
+        let num_bytes = bit_util::ceil(data_len, 8);
+        let mut null_buf = MutableBuffer::new(num_bytes).with_bitset(num_bytes, false);
+        let mut val_buf = MutableBuffer::new(
+            data_len * mem::size_of::<<T as ArrowPrimitiveType>::Native>(),
+        );
+
+        let null = vec![0; mem::size_of::<<T as ArrowPrimitiveType>::Native>()];
+
+        let null_slice = null_buf.data_mut();
+        iter.enumerate().for_each(|(i, item)| {
+            if let Some(a) = item.borrow() {
+                bit_util::set_bit(null_slice, i);
+                val_buf.write_all(a.to_byte_slice()).unwrap();
+            } else {
+                val_buf.write_all(&null).unwrap();
+            }
+        });
+
+        let data = ArrayData::new(
+            T::get_data_type(),
+            data_len,
+            None,
+            Some(null_buf.freeze()),
+            0,
+            vec![val_buf.freeze()],
+            vec![],
+        );
+        PrimitiveArray::from(Arc::new(data))
+    }
+}
+
 // TODO: the macro is needed here because we'd get "conflicting implementations" error
 // otherwise with both `From<Vec<T::Native>>` and `From<Vec<Option<T::Native>>>`.
 // We should revisit this in future.
@@ -713,34 +769,7 @@ macro_rules! def_numeric_from_vec {
             for PrimitiveArray<$ty>
         {
             fn from(data: Vec<Option<<$ty as ArrowPrimitiveType>::Native>>) -> Self {
-                let data_len = data.len();
-                let mut null_buf = make_null_buffer(data_len);
-                let mut val_buf = MutableBuffer::new(
-                    data_len * mem::size_of::<<$ty as ArrowPrimitiveType>::Native>(),
-                );
-
-                {
-                    let null =
-                        vec![0; mem::size_of::<<$ty as ArrowPrimitiveType>::Native>()];
-                    let null_slice = null_buf.data_mut();
-                    for (i, v) in data.iter().enumerate() {
-                        if let Some(n) = v {
-                            bit_util::set_bit(null_slice, i);
-                            // unwrap() in the following should be safe here since we've
-                            // made sure enough space is allocated for the values.
-                            val_buf.write_all(&n.to_byte_slice()).unwrap();
-                        } else {
-                            val_buf.write_all(&null).unwrap();
-                        }
-                    }
-                }
-
-                let array_data = ArrayData::builder($ty::get_data_type())
-                    .len(data_len)
-                    .add_buffer(val_buf.freeze())
-                    .null_bit_buffer(null_buf.freeze())
-                    .build();
-                PrimitiveArray::from(array_data)
+                PrimitiveArray::from_iter(data.iter())
             }
         }
     };

rust/arrow/src/array/iterator.rs

@@ -0,0 +1,85 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use crate::datatypes::ArrowPrimitiveType;
+
+use super::{Array, PrimitiveArray, PrimitiveArrayOps};
+
+/// an iterator that returns Some(T) or None, that can be used on any non-boolean PrimitiveArray
+#[derive(Debug)]
+pub struct PrimitiveIter<'a, T: ArrowPrimitiveType> {
+    array: &'a PrimitiveArray<T>,
+    i: usize,
+    len: usize,
+}
+
+impl<'a, T: ArrowPrimitiveType> PrimitiveIter<'a, T> {
+    /// create a new iterator
+    pub fn new(array: &'a PrimitiveArray<T>) -> Self {
+        PrimitiveIter::<T> {
+            array,
+            i: 0,
+            len: array.len(),
+        }
+    }
+}
+
+impl<'a, T: ArrowPrimitiveType> std::iter::Iterator for PrimitiveIter<'a, T> {
+    type Item = Option<T::Native>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let i = self.i;
+        if i >= self.len {
+            None
+        } else if self.array.is_null(i) {
+            self.i += 1;
+            Some(None)
+        } else {
+            self.i += 1;
+            Some(Some(self.array.value(i)))
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.len, Some(self.len))
+    }
+}
+
+/// all arrays have known size.
+impl<'a, T: ArrowPrimitiveType> std::iter::ExactSizeIterator for PrimitiveIter<'a, T> {}
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Arc;
+
+    use crate::array::{ArrayRef, Int32Array};
+
+    #[test]
+    fn test_primitive_array_iter_round_trip() {
+        let array = Int32Array::from(vec![Some(0), None, Some(2), None, Some(4)]);
+        let array = Arc::new(array) as ArrayRef;
+
+        let array = array.as_any().downcast_ref::<Int32Array>().unwrap();
+
+        // to and from iter, with a +1
+        let result: Int32Array =
+            array.iter().map(|e| e.and_then(|e| Some(e + 1))).collect();
+
+        let expected = Int32Array::from(vec![Some(1), None, Some(3), None, Some(5)]);
+        assert_eq!(result, expected);
+    }
+}

rust/arrow/src/array/mod.rs

@@ -87,6 +87,7 @@ mod builder;
 mod cast;
 mod data;
 mod equal;
+mod iterator;
 mod null;
 mod ord;
 mod union;
@@ -239,6 +240,10 @@ pub type DurationMillisecondBuilder = PrimitiveBuilder<DurationMillisecondType>;
 pub type DurationMicrosecondBuilder = PrimitiveBuilder<DurationMicrosecondType>;
 pub type DurationNanosecondBuilder = PrimitiveBuilder<DurationNanosecondType>;
 
+// --------------------- Array Iterator ---------------------
+
+pub use self::iterator::*;
+
 // --------------------- Array Equality ---------------------
 
 pub use self::equal::ArrayEqual;