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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/01/31 15:29:49 UTC

[GitHub] [arrow] Dandandan opened a new pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Dandandan opened a new pull request #9381:
URL: https://github.com/apache/arrow/pull/9381


   This adds a `shift` function (now only accept primitive arrays) that shifts an array left or right by `offset`.
   
   This is something that could be used to implement `LAG` `LEAD` etc. in DataFusion and other crates.


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[GitHub] [arrow] ritchie46 edited a comment on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
ritchie46 edited a comment on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771805111


   
   _edit_: The shift direction is opposite to what pandas has implemented though. In Polars I have followed pandas' direction:
   
   that a positive input shifts values to the right.
   
   as it seemed intuitive to me as well. I don't know what other tools do.


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[GitHub] [arrow] alamb commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-774316829


   I think this one is ready to go -- I'll plan to merge it tomorrow unless someone else beats me to it


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[GitHub] [arrow] alamb closed pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb closed pull request #9381:
URL: https://github.com/apache/arrow/pull/9381


   


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[GitHub] [arrow] jorgecarleitao commented on a change in pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
jorgecarleitao commented on a change in pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#discussion_r571416880



##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,110 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+/// A positive value for `offset` shifts the array to the right
+/// a negative value shifts the array to the left.
+/// # Examples
+/// ```
+/// use arrow::array::Int32Array;
+/// use arrow::error::Result;
+/// use arrow::compute::shift;
+///
+/// let a: Int32Array = vec![Some(1), None, Some(4)].into();
+/// // shift array 1 element to the right
+/// let res = shift(&a, 1).unwrap();
+/// let expected: Int32Array = vec![None, Some(1), None].into();
+/// assert_eq!(res.as_ref(), &expected)
+/// ```
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(-offset, 0, values.len() as i64) as usize;
+    let length = values.len() - abs(offset) as usize;
+    let slice = values.slice(slice_offset, length);
+
+    // Generate array with remaining `null` items
+    let nulls = abs(offset as i64) as usize;
+
+    let mut null_array = MutableBuffer::new(nulls);
+    let mut null_data = MutableBuffer::new(nulls * T::get_byte_width());
+    null_array.extend_zeros(nulls);
+    null_data.extend_zeros(nulls * T::get_byte_width());
+
+    let null_data = ArrayData::new(
+        T::DATA_TYPE,
+        nulls as usize,
+        Some(nulls),
+        Some(null_array.into()),

Review comment:
       I did not have time to go through this, but I get the feeling that this buffer may be too large: imo it should be `ceil(nulls, 8)`, since there are 8 slots per byte for bitmaps, no?




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[GitHub] [arrow] Dandandan commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
Dandandan commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771913447


   Hm, interesting indeed @ritchie46 I wrongly assumed that was pandas approach, but I now realize I recently saw `shift(1)` being used for implementing something similar to `LAG`. We should do whatever is standard I would say, maybe we should look at some other libraries as well.


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[GitHub] [arrow] alamb commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-774456614


   Thanks again @Dandandan 


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[GitHub] [arrow] Dandandan commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
Dandandan commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-773986297


   I agree it is best to have the order the same as pandas, it also seems other libraries do LAG / right shift for positive values as well.
   
   Cleaned it up a bit, added a doc test.
   


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[GitHub] [arrow] alamb commented on a change in pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on a change in pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#discussion_r570891227



##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)

Review comment:
       I wonder if you can add a doc example here, something like https://github.com/apache/arrow/blob/master/rust/arrow/src/compute/kernels/take.rs#L62-L76 just to show the behavior (lifting / simplifying one of unit tests is probably a good level)

##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(offset, 0, values.len() as i64) as usize;
+    let length = values.len() - abs(offset) as usize;
+    let slice = values.slice(slice_offset, length);
+
+    // Generate array with remaining `null` items
+    let nulls = abs(offset as i64) as usize;
+
+    let mut null_array = MutableBuffer::new(nulls);
+    let mut null_data = MutableBuffer::new(nulls * T::get_byte_width());
+    null_array.extend_zeros(nulls);
+    null_data.extend_zeros(nulls * T::get_byte_width());
+
+    let null_data = ArrayData::new(
+        T::DATA_TYPE,
+        nulls as usize,
+        Some(nulls),
+        Some(null_array.into()),
+        0,
+        vec![null_data.into()],
+        vec![],
+    );
+
+    // Concatenate both arrays, add nulls after if shift > 0 else before
+    let null_arr = make_array(Arc::new(null_data));
+    if offset > 0 {
+        concat(&[slice.as_ref(), null_arr.as_ref()])
+    } else {
+        concat(&[null_arr.as_ref(), slice.as_ref()])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::array::Int32Array;
+
+    use super::*;
+
+    #[test]
+    fn test_shift_neg() {
+        let a: Int32Array = vec![Some(1), None, Some(4)].into();
+        let res = shift(&a, -1).unwrap();
+
+        let b = res.as_any().downcast_ref::<Int32Array>().unwrap();
+        assert_eq!(a.len(), res.len());
+        assert_eq!(false, b.is_valid(0));
+        assert_eq!(1, b.value(1));
+        assert_eq!(false, b.is_valid(2));

Review comment:
       ```suggestion
           let expected: Int32Array = vec![None, Some(1), None].into();
   
           assert_eq!(b, &expected);
   ```

##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)

Review comment:
       It might also be good to specify what happens if you shift by more than the size of the array (e.g. that there is no error, just the entire array is returned as null)

##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(offset, 0, values.len() as i64) as usize;
+    let length = values.len() - abs(offset) as usize;
+    let slice = values.slice(slice_offset, length);
+
+    // Generate array with remaining `null` items
+    let nulls = abs(offset as i64) as usize;
+
+    let mut null_array = MutableBuffer::new(nulls);
+    let mut null_data = MutableBuffer::new(nulls * T::get_byte_width());
+    null_array.extend_zeros(nulls);
+    null_data.extend_zeros(nulls * T::get_byte_width());
+
+    let null_data = ArrayData::new(
+        T::DATA_TYPE,
+        nulls as usize,
+        Some(nulls),
+        Some(null_array.into()),
+        0,
+        vec![null_data.into()],
+        vec![],
+    );
+
+    // Concatenate both arrays, add nulls after if shift > 0 else before
+    let null_arr = make_array(Arc::new(null_data));
+    if offset > 0 {
+        concat(&[slice.as_ref(), null_arr.as_ref()])
+    } else {
+        concat(&[null_arr.as_ref(), slice.as_ref()])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::array::Int32Array;
+
+    use super::*;
+
+    #[test]
+    fn test_shift_neg() {
+        let a: Int32Array = vec![Some(1), None, Some(4)].into();
+        let res = shift(&a, -1).unwrap();
+
+        let b = res.as_any().downcast_ref::<Int32Array>().unwrap();
+        assert_eq!(a.len(), res.len());
+        assert_eq!(false, b.is_valid(0));
+        assert_eq!(1, b.value(1));
+        assert_eq!(false, b.is_valid(2));
+    }
+
+    #[test]
+    fn test_shift_pos() {
+        let a: Int32Array = vec![Some(1), None, Some(4)].into();
+        let res = shift(&a, 1).unwrap();
+
+        let b = res.as_any().downcast_ref::<Int32Array>().unwrap();
+        assert_eq!(a.len(), res.len());
+        assert_eq!(false, b.is_valid(0));
+        assert_eq!(4, b.value(1));
+        assert_eq!(false, b.is_valid(2));

Review comment:
       ```suggestion
           let expected: Int32Array = vec![None, Some(1), None].into();
   
           assert_eq!(b, &expected);
   ```

##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(offset, 0, values.len() as i64) as usize;
+    let length = values.len() - abs(offset) as usize;
+    let slice = values.slice(slice_offset, length);
+
+    // Generate array with remaining `null` items
+    let nulls = abs(offset as i64) as usize;
+
+    let mut null_array = MutableBuffer::new(nulls);
+    let mut null_data = MutableBuffer::new(nulls * T::get_byte_width());
+    null_array.extend_zeros(nulls);
+    null_data.extend_zeros(nulls * T::get_byte_width());
+
+    let null_data = ArrayData::new(
+        T::DATA_TYPE,
+        nulls as usize,
+        Some(nulls),
+        Some(null_array.into()),
+        0,
+        vec![null_data.into()],
+        vec![],
+    );
+
+    // Concatenate both arrays, add nulls after if shift > 0 else before
+    let null_arr = make_array(Arc::new(null_data));
+    if offset > 0 {
+        concat(&[slice.as_ref(), null_arr.as_ref()])
+    } else {
+        concat(&[null_arr.as_ref(), slice.as_ref()])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::array::Int32Array;
+
+    use super::*;
+
+    #[test]
+    fn test_shift_neg() {
+        let a: Int32Array = vec![Some(1), None, Some(4)].into();
+        let res = shift(&a, -1).unwrap();
+
+        let b = res.as_any().downcast_ref::<Int32Array>().unwrap();
+        assert_eq!(a.len(), res.len());
+        assert_eq!(false, b.is_valid(0));
+        assert_eq!(1, b.value(1));
+        assert_eq!(false, b.is_valid(2));

Review comment:
       FWIW I agree with @ritchie46  that I expect `shift([1,NULL,4], -1)` to shift LEFT -- so `[NULL, 4, NULL]` rather than right ( aka [NULL, 1, NULL]`)
   
   I don't think Postgres has any similar function I could find to guide us. I would vote to be consistent with Pandas -- which appears to shift right with a positive shift: https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.shift.html




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[GitHub] [arrow] ritchie46 commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
ritchie46 commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771805111


   LGTM


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[GitHub] [arrow] nevi-me commented on a change in pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
nevi-me commented on a change in pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#discussion_r570614353



##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(offset, 0, values.len() as i64) as usize;

Review comment:
       This is very neat :)




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[GitHub] [arrow] codecov-io commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
codecov-io commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-770402549


   # [Codecov](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=h1) Report
   > Merging [#9381](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=desc) (3cfc067) into [master](https://codecov.io/gh/apache/arrow/commit/b18c5677ecc5058333b69d08f82b267f79d2df8d?el=desc) (b18c567) will **increase** coverage by `0.05%`.
   > The diff coverage is `100.00%`.
   
   [![Impacted file tree graph](https://codecov.io/gh/apache/arrow/pull/9381/graphs/tree.svg?width=650&height=150&src=pr&token=LpTCFbqVT1)](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=tree)
   
   ```diff
   @@            Coverage Diff             @@
   ##           master    #9381      +/-   ##
   ==========================================
   + Coverage   81.96%   82.02%   +0.05%     
   ==========================================
     Files         230      231       +1     
     Lines       53374    53520     +146     
   ==========================================
   + Hits        43750    43898     +148     
   + Misses       9624     9622       -2     
   ```
   
   
   | [Impacted Files](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=tree) | Coverage Δ | |
   |---|---|---|
   | [rust/arrow/src/compute/kernels/window.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9hcnJvdy9zcmMvY29tcHV0ZS9rZXJuZWxzL3dpbmRvdy5ycw==) | `100.00% <100.00%> (ø)` | |
   | [rust/arrow/src/compute/kernels/concat.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9hcnJvdy9zcmMvY29tcHV0ZS9rZXJuZWxzL2NvbmNhdC5ycw==) | `100.00% <0.00%> (ø)` | |
   | [rust/parquet/src/encodings/encoding.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9wYXJxdWV0L3NyYy9lbmNvZGluZ3MvZW5jb2RpbmcucnM=) | `95.05% <0.00%> (+0.19%)` | :arrow_up: |
   | [rust/arrow/src/array/transform/mod.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9hcnJvdy9zcmMvYXJyYXkvdHJhbnNmb3JtL21vZC5ycw==) | `93.20% <0.00%> (+0.27%)` | :arrow_up: |
   | [rust/arrow/src/array/transform/structure.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9hcnJvdy9zcmMvYXJyYXkvdHJhbnNmb3JtL3N0cnVjdHVyZS5ycw==) | `83.33% <0.00%> (+3.33%)` | :arrow_up: |
   | [rust/arrow/src/array/transform/fixed\_binary.rs](https://codecov.io/gh/apache/arrow/pull/9381/diff?src=pr&el=tree#diff-cnVzdC9hcnJvdy9zcmMvYXJyYXkvdHJhbnNmb3JtL2ZpeGVkX2JpbmFyeS5ycw==) | `84.21% <0.00%> (+5.26%)` | :arrow_up: |
   
   ------
   
   [Continue to review full report at Codecov](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=continue).
   > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
   > `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
   > Powered by [Codecov](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=footer). Last update [b18c567...3cfc067](https://codecov.io/gh/apache/arrow/pull/9381?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
   


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[GitHub] [arrow] ritchie46 commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
ritchie46 commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771805111


   LGTM


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[GitHub] [arrow] Dandandan commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
Dandandan commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771913447


   Hm, interesting indeed @ritchie46 I wrongly assumed that was pandas approach, but I now realize I recently saw `shift(1)` being used for implementing something similar to `LAG`. We should do whatever is standard I would say, maybe we should look at some other libraries as well.


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[GitHub] [arrow] nevi-me commented on a change in pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
nevi-me commented on a change in pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#discussion_r570614353



##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,100 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+pub fn shift<T>(values: &PrimitiveArray<T>, offset: i64) -> Result<ArrayRef>
+where
+    T: ArrowPrimitiveType,
+{
+    // Compute slice
+    let slice_offset = clamp(offset, 0, values.len() as i64) as usize;

Review comment:
       This is very neat :)




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[GitHub] [arrow] github-actions[bot] commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-770400024


   https://issues.apache.org/jira/browse/ARROW-11447


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[GitHub] [arrow] alamb commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-773990003


   Looking good -- thanks @Dandandan 


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[GitHub] [arrow] alamb commented on a change in pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on a change in pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#discussion_r570918542



##########
File path: rust/arrow/src/compute/kernels/window.rs
##########
@@ -0,0 +1,110 @@
+// 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.
+
+//! Defines windowing functions, like `shift`ing
+
+use crate::compute::concat;
+use num::{abs, clamp};
+use std::sync::Arc;
+
+use crate::{
+    array::{make_array, ArrayData, PrimitiveArray},
+    datatypes::ArrowPrimitiveType,
+    error::Result,
+};
+use crate::{
+    array::{Array, ArrayRef},
+    buffer::MutableBuffer,
+};
+
+/// Shifts array by defined number of items (to left or right)
+/// A positive value for `offset` shifts the array to the left (LAG)
+/// a negative value shifts the array to the left.
+/// # Examples
+/// ```
+/// use arrow::array::Int32Array;
+/// use arrow::error::Result;
+/// use arrow::compute::shift;
+///
+/// let a: Int32Array = vec![Some(1), None, Some(4)].into();
+/// // shift array 1 element to the left

Review comment:
       ```suggestion
   /// // shift array 1 element to the right
   ```




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[GitHub] [arrow] ritchie46 edited a comment on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
ritchie46 edited a comment on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771805111






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[GitHub] [arrow] ritchie46 edited a comment on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
ritchie46 edited a comment on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-771805111


   LGTM
   
   _edit_: The shift direction is opposite to what pandas has implemented though. In Polars I have followed pandas' direction:
   
   that a positive input shifts values to the right.
   
   as it seemed intuitive to me as well. I don't know what other tools do.


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[GitHub] [arrow] alamb commented on pull request #9381: ARROW-11447: [Rust] Add shift kernel for primitive types

Posted by GitBox <gi...@apache.org>.
alamb commented on pull request #9381:
URL: https://github.com/apache/arrow/pull/9381#issuecomment-774258321


   Looks like there is an error in the simd tests: https://github.com/apache/arrow/pull/9381/checks?check_run_id=1838559432
   
   ```
   
   
   ---- src/compute/kernels/window.rs - compute::kernels::window::shift (line 38) stdout ----
   error[E0615]: attempted to take value of method `as_ref` on type `Arc<dyn Array>`
     --> src/compute/kernels/window.rs:47:16
      |
   12 | assert_eq!(res.as_ref, &expected)
      |                ^^^^^^ method, not a field
      |
   help: use parentheses to call the method
      |
   12 | assert_eq!(res.as_ref(), &expected)
      |                      ^^
   
   ```


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